T. Bronté Evermann, Harry Warren, S. S. Chadwick, Leonard Young, Wm. F. Hill, Millard Knowlton, Robert Gillum, and Dr. C. B. Wilson. The work was carried on mostly in the summer and fall, but something was done each month of the year.

The Bureau of Fisheries undertook the investigations at Lake Maxinkuckee through realizing the importance to fish culture of an exact knowlege of the physical and biological conditions in the different types of lakes and streams of the country including the small inland lakes of glacial origin like Lake Maxinkuckee. With reference to the importance of these investigations the authors say:

With scarcely an exception these lakes teem with food and game fishes of the finest quality, besides many other species of greater or less importance. Many of these lakes are inhabited also by a large number of species of turtles, batrachians, mollusks and crustaceans, some of which are already used for food or otherwise utilized by man. They are the home also of many other species of aquatic animals and many species of aquatic plants which are known to serve an important purpose in the economy of the lakes in their relation to food fishes, and of still many other species whose status we do not yet know. The value of exact knowledge concerning this type of lake and the inhabitants thereof is appreciated by all biologists and fish culturists and can scarcely be overestimated.

Lake Maxinkuckee was chosen for special and detailed study principally for the following reasons: it was of suitable size, not being too large for any of its parts to be reached readily from a central station; the tributary waters were not of such large size as to "complicate the problem"; it was a fairly "homogeneous environmental unit"; there are fishing and angling interests there; it appeared to be "typical of the class of small glacial lakes "; it was easily accessible; and field expenses there were especially small.

The purposes of this work were chiefly three: (1) "To gain a fairly good understanding of the physical and biological conditions obtaining in a typical glacial lake. Accurate knowledge of one lake of a type enables

a study of other lakes of that type to be made more readily and easily." (2) "To study carefully the physical and biological conditions under which the more important of the species thrive." (3) "To study carefully and fully the habits of as many species of animals and plants of the lake as time permitted."

The treatment is under two main topics: (1) Physical Features and (2) Biology. Under the first are discussed in some two hundred pages the location, size, form, depth, bottom topography, soils, lake tributaries, character of the surrounding country, and weather conditions. Under the topic, Biology, are taken up, first, a consideration of the five classes of vertebrate animals represented in the region with a general introductory discussion of each followed by descriptions of the species found, and secondly (in Volume 2) similar discussions of the invertebrates and plants.

Fish naturally receive most attention and 213 pages are given to this group. The account is a useful one, not only for zoologists but for others likely to read or consult the work, since the majority of the 64 species described are very generally distributed in such lakes, and at least two dozen of them are well known to most anglers. The discussions deal with the species found, and for each are given notes on its status in the region and structural details of taxonomic interest, and for most of them facts on behavior, food, enemies, angling, and economic importance are included.

The data on the food of the fish are important. Although these are chiefly qualitative in character, they are of considerable ecological value. Determinations of the percentages of the different food materials in the digestive tracts may still be made, since it is probable that these were preserved. However, no reference can be found concerning the disposition of the food collections or other collections made during the progress of the survey of the Maxinkuckee region. There is a detailed account with list of species of each collection made at each of the many numbered stations; and it would have been important to have stated where these collec

tions are available for future workers in the region or by specialists on the different groups represented in them.

Preceding the annotated list there is a lengthy general discussion describing collecting methods, conditions for fish life at the lake, migrations and seasonal movements, fishing, fish protection, and fish planting. A three-page table with the results of dredging is of considerable biological interest, and there are two other tables, which are especially unique and interesting. One of the two shows the number of fish taken by a single angler during nine months and the other the number of boats seen on the lake correlated with weather conditions during two summer months. A part of this discussion of fishes is a fifteen-page contribution by Charles B. Wilson on 66 Food and Parasites of Fishes."

The treatment of the fish of the region is followed by that of mammals. Why the mammals are taken up here is apparently not explained. Thirty species are listed with many notes. The ones having the most direct relation to the life of the lake are muskrats, minks, otters, and raccoons. There is a long account of the muskrat, which is a very positive contribution to its natural history, and the data given on the numbers caught there by trappers will be useful in estimating the value of the small inland lakes as a source of muskrat fur.

The ninety pages of information on the birds include an annotated list of 175 species. At least fifty of these were found to be very directly and closely related ecologically to the fish and other organisms of the lake. The number of aquatic and shore birds is large and the total of their influence upon the life of the lake is considered to be great. Some food studies of water birds contribute to the meager knowledge of the relation of these birds to fish. The twelve pages on the coot are an important addition to the literature of this unique water bird.

The reptiles are treated in about forty pages and they seem to be of little importance in the biology of the lake except the turtles, which were important as scavengers. De

tailed shell measurements and weights are recorded for 225 examples of four species of turtles.

The water dog (Necturus maculosus) was worthy of more consideration than any of the other 18 kinds of amphibians found, and it is concluded from food studies of the water dog that, of all the animals inhabiting the lake, it was the worst enemy of fish.

The material gathered concerning the invertebrates and plants of the Maxinkuckee region composes the second volume. The slight attention that could be given to a group so abundantly represented and so important causes a disappointment. The May-flies and dragon-flies were found to be of special importance to the fish of the lake. A list of 56 species of dragon-flies with important notes is given, and this was formed through the help of Mr. E. B. Williamson. Notes on life-histories, behavior, and ecology are given on many other forms. A notable contribution showing the value of chironomid larvæ as fish food comes from the finding of "almost a bucketful" of them in a 75-pound buffalofish (Ictiobus cyprinella).

The mollusks follow the insects but precede the other arthropods, an arrangement which is confusing. Mussels are fully discussed with much attention to the fourteen local forms, with many data on their food, enemies, diseases, and reproduction. The 116 other species of mollusks are listed without notes.

The account of the Crustacea of the lake is based largely on the plankton studies made. there by Professor Juday and the investigations on the parasitic copepods by Dr. Wilson and of the crawfish by Professor William P. Hay. The inference "that plankton species of crustaceans constitute a large part, probably nearly all, of the first food of young fishes, and much of the food of some fishes throughout their entire lives" serves to corroborate a similar conclusion concerning the food of fish derived from the study of Illinois fish by Dr. S. A. Forbes.

The eleven species of leeches, which form a "fairly conspicuous part of the lake fauna " are discussed by Professor J. Percy Moore, of

the University of Pennsylvania. They infested fish, turtles, mussels, and snails. One species (Dina fervida) appears to be a scavenger only.

Little attention was given to the worms other than the leeches, and these with the sponges and protozoans are considered in only nine pages.

About three fifths of the second volume treats of the plants of Lake Maxinkuckee and vicinity, particularly with the aquatic forms. In addition to annotated lists of species there are important general discussions of such subjects as the uses of water plants to the other organisms of the lake and of the floral regions; the latter were found to be as follows: Beach; lake plains; low woodland; upland clay woodland; upland loamy woodland; gullies; woodland ponds; peat bogs; and shifting sand regions. No reference appears to be made to fungi, although it is well known that some forms like Saprolegnia attack fish.

Throughout the treatment of the plants of the region, there is much on their relation to fish and other life of the lake; and it is noted that:

While the division line between the lake flora and the land flora is in most cases pretty sharply drawn, it is not easy to tell where the boundary line lies between plants having some influence upon the lake and those which have none, if there be such.

The grouping of species in the lists of water plants is puzzling and perplexing till one reads the easily overlooked explanation on page 135, where we are informed that floating plants are first disposed of and then those of the deeper water, proceeding from thence to the shallow water. In this arrangement species of a genus and sometimes subspecies of a species are separated. This is likely to be annoying to the taxonomist but not to students of ecology or plant distribution.

Only the first volume of the work has illustrations, and nearly all of these are of fish, there being a few of frogs, and some general views loaned by the Culver Military Academy. The latter are not numbered or referred to in the list of illustrations.

The well-reproduced colored drawings, mostly from Forbes and Richardson's "Fishes of Illinois," give considerable attractiveness to the publication and also add to its scientific value since the fish are very accurately shown.

There is a large folded map in the back of the first volume. This has a scale of 400 feet to the inch and gives bottom contour lines for every difference of ten feet and for the depths 85 and 88 feet, 89 feet being the maximum depth found.

The books are well printed in a large, clear type on good, heavy paper, and there are very few typographical errors. All through the work is evidence of much painstaking. The binding is in good cloth. Withal they make an attractive addition to the naturalist's library as well as a useful publication for his reference and study.

T. L. HANKINSON

THE ROOSEVELT WILD LIFE FOREST EXPERIMENT STATION, SYRACUSE, N. Y.

SPECIAL ARTICLES

AN EXPLANATION OF LIESEGANG'S RINGS

3

RAPHAEL ED. LIESEGANG in 18981 published results showing that when silver nitrate solution is placed on a gelatine gel containing potassium bichromate, there develops on standing a series of concentric precipitations of silver chromate.2 These zones are known as Liesegang's rings. Wilhelm Ostwald published an explanation of the formation of these rings which was accepted until Liesegang, Bechold, and Hatschek cited experiments which showed it untenable. Ostwald's explanation is briefly: Under certain conditions supersaturated solutions are formed, and when solid crystals or nuclei

1 Liesegang, Zeit f. Phys. Chemie, 1907, 59, 444. 2 For details see Ostwald-Fischer, "Theoretical and Applied Colloid Chemistry," Wiley and Sons, New York, 1918.

3 Ostwald, "Lehrbuch der Allg. Chemie" (2 aufl.), II., 778.

chromate in the region lasts until all the soluble silver is precipitated. Then the silver salt wanders out over the ring into the chromate gelation until a new supersaturated region is formed and the precipitation process is repeated.

The main objection to Ostwald's explanation is that a supersaturated condition has been shown unnecessary for ring formation; also that there are other factors involved in the ring formation. Since no explanation has been accepted, I wish to present one which seems adequate.

The chromate in the gelatine is relatively fixed and diffuses very slowly; when AgNO, is added, there is an immediate formation of silver chromate not only under the silver so

lution but there is a sphere of influence which can be seen with the aid of a hand lens (see A figure). The silver attracts the chromate from this area and leaves it sharply demarcated. This demarcation could be due to the withdrawal of the chromate or it might be due to the influence of the potassium nitrate formed in the reaction. However, the amount of potassium nitrate that could be formed has no such influence on the gelatine chromate; and an experiment can be devised to show that there is no chromate, or very little of it, in this zone. The experiment is as follows: Place a minute droplet of silver nitrate on a gelatin plate until the zone of influence is distinct. Then at a short distance from it place a large drop of silver nitrate (B) sufficiently large so that when the Liesegang rings are formed they will include the smaller drop. After a time a condition develops as shown in figure where the larger circles are interrupted by the zone of influence of the smaller particle. This shows that there is not enough chromate to precipitate; it has all been attracted by the first silver nitrate. The explanation of Liesegang ring formation then is as follows:

Silver chromate is formed and a clear zone results in the gelatine by the attraction of the chromate to the silver. Beyond this zone of influence, the chromate is fixed and remains so unless an attraction force is exerted. The silver nitrate now wanders out through the ring into the clear zone until it approximates the chromate gelatine sufficiently close to exert an attraction force which again draws the chromate and forms another ring and clear zone. At the same time the chromate exerts a pull on the silver and the ring is formed where the forces are balanced. Again it may be presumed that to start the chromate moving, will require a greater force than to keep it moving after the start is made, consequently the second ring is separated from the first.

With each succeeding ring the concentration of the silver is less and this will also operate to remove the succeeding rings farther and farther apart. Ring formation by these or by other reagents depends on or is modified by

other conditions which are however of secondary importance. As a requisite, the precipitate formed must be permeable to the liquid solution used; in this case the silver nitrate. If for example, lead acetate be used instead of silver nitrate no ring formation occurs, because the lead chromate under these conditions is impervious to lead acetate. Not only is it impervious to lead acetate but if silver nitrate replace the solution of lead acetate after the precipitate of lead chromate is formed, silver nitrate will not penetrate the lead chromate wall, and no ring formation will occur. For the same reason if the silver nitrate and potassium bichromate solutions are reversed, no ring formation will occur. HUGH MCGUIGAN

COLLEGE OF MEDICINE,
UNIVERSITY OF ILLINOIS

THE NORTH CAROLINA ACADEMY OF

SCIENCE

THE twentieth annual meeting of the North Carolina Academy of Science was held on April 29 and 30, 1921, at Wake Forest College, Wake Forest, N. C., with about 50 members present, and the following program was carried out.

Presidential address. The age of insects, Professor Z. P. Metcalf, State College.

PAPERS

The genus Raspaillia and the independent variability of diagnostic features: H. V. WILSON.

Current research in organic chemistry at the University of North Carolina: A. S. WHEELER. Judgments of length, mass and time: A. H. PATTERSON.

A photometric study of the fluorescence of iodine vapor: W. E. SPEAS.

Some fungi new to North America or the South: W. C. COKER.

Breeding results from overwintering cocoons of the Polyphemus moth: C. S. BRIMLEY.

On the polyembryonic development_of_the_parasite, Copidosoma gelechiae Howard: R. W. LEIBY. New North Carolina gall types: B. W. WELLS. The Lorentz transformation in Einstein relativity: ARCHIBALD HENDERSON.

Solid culture media with a wide range of hydrogen and hydroxyl ion concentration: F. A. WOLF and I. V. SHUNK.

Notes on the ecology and life history of the Texas horned lizard: J. P. GIVLER.

Ionizing potentials of gases by negative electrons: A. A. DIXON.

An interesting anomaly in the pulmonary veins of man: W. C. GEORGE.

The inheritance of economic qualities in cotton: R. Y. WINTERS.

Questions arising from the discovery of occasional vertebrate hermaphrodites, with a demonstration of a case in a pig: HARLEY N. GOULD. (Lantern.)

The artificial incubation of turtle eggs: BERT CUNNINGHAM. (Lantern.)

Effects of desiccation on cotton seeds and the seed-borne element of cotton anthracnose: S. C. LEHMAN.

The anatomy of Angiopteris: H. L. BLOMQUIST. (Lantern.)

The electron, its measurements and applications: J. B. DERIEUX. (Lantern.)

Further studies on the pure culture of diatoms: BERT CUNNINGHAM and J. T. BARNES. (Lantern.)

Aphidius, a parasite of the cotton louse: H. SPENCER.

From egg to frog in two months: H. V. WILSON. Some considerations in defense of the general biology course: J. P. GIVLER.

Some questions concerning the teaching of physics in North Carolina: C. W. EDWARDS.

Notes on the salamanders of the Cayuga Lake Basin, N. Y., with reference to eggs and larvæ: JULIA MOESEL HABER.

A more remarkable shoot: WILLIAM F. PROUTY. Relationship of temperature and relative hu midity to the distribution of cockroaches: V. R. HABER.

Recent views on the nutritive properties of milk: J. O. HALVERSON.

Notes on recently discovered Miocene whale: WILLIAM F. PROUTY.

A method of differentiating mucous and serous cells: MISS E. G. CAMPBELL.

DEMONSTRATIONS

reared

Metamorphosed frogs (Chorophilus), from artificially inseminated eggs in two months: H. V. WILSON.

New North Carolina galls: B. W. WELLS.
Shells of Raleigh turtles: C. S. BRIMLEY.
Examples of Fulgorida: Z. P. METCALF.

At the business meeting President Metcalf announced that affiliation with the American Association for the Advancement of Science has been completed except for official notice from the Permanent Secretary of the Association.

The following officers were elected for the ensuing year: president, Jas. L. Lake, professor of physics, Wake Forest College; vice-president, Dr. J. H. Pratt, state geologist; secretary-treasurer, Bert Cunningham, professor of biology, Trinity College; additional members of the Executive Committee, H. R. Totten, University of North Carolina, R. N. Wilson, Trinity College, and F. A. Wolf, State College.

C. S. BRIMLEY, Acting Secretary