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the mode of production by division of the Desmids. He observed the process in Euglypha alveolata, and found it similar to the multiplication of Chlamydophrys, as already noticed by Cienkowsky.

Supposed Radiolarians and Diatomacea of the Coal-Measures.

At the Dublin meeting of the British Association, Professor W. C. Williamson called attention to the Traquaria of Mr. Carruthers, which were found in the lower coalmeasures of Lancashire and Yorkshire, with small spherical objects supposed to be Radiolarians. After thorough examination, Professor Williamson rejects the idea of their Radiolarian character; while their close organic resemblance to some obviously vegetable conceptacles found in the same coal-measures suggested that the Traquariæ are also vegetable structures.

Count Castracane having published an account of a process by which he reduced numerous specimens of coals to very minute quantities of coal-ash, in which he found numerous marine and fresh-water Diatomaceæ, Professor Roscoe detailed one of his ablest assistants, in his laboratory at Owens College, to prepare analyses of a number of coals according to Count Castracane's method. The residual ashes were mounted microscopically and examined by Professor Williamson, and in no one of them could a trace of a diatom be discovered. It has long been suspected by microscopists interested in the study of these minute organisms that the Italian observer was misled by the accidental introduction of modern forms somewhere during the treatment. It is well known that, even after repeated washings and rinsings of test-tubes and bottles, diatoms will still cling to the sides, and becoming afterwards dislodged, make their appearance in other preparations placed in the same tubes or bottles.

Revivification of Diatoms.

M. Paul Petit states that, having collected diatoms at various times of the year, with their substratum of mud, and allowed them to dry in the sun for six or eight months, he had placed them in distilled water well aerated, and found that in four days many of the frustules, which showed before only large brown granules, began to have these granules aug

mented in volume, and at the end of five days the frustules were half filled, and the characteristic yellow tint of the endochrome appeared; on the eighth day the revivification was complete, and soon after they began their curious motions, and the multiplication by division (Journal de Micrographie, Dec., 1877).

In connection with the above, Mr. Fred. Habirshaw, of New York, states that in 1871 Capt. Mortimer brought from San Francisco, in his ship, a large bottle of diatoms (from fresh water). When he arrived in England they were still alive, but afterwards dried up, and remained in that state in his cabin until the summer of 1877-a period of six years. "Having found the old bottle, which we knew very well, we refilled it with water, and on examining it several days later we found some living specimens in it.”

That living diatoms were found as stated there can be no doubt, but that they were revivified yet needs proof. It is contrary to experience hitherto; indeed, it is well known, and one of the means employed to procure purer gatherings, that oftentimes apparently pure water will, if allowed to stand quietly, show an abundant crop of diatoms. In many cases that we have noted of the appearance of living diatoms, after wetting long-dried material, they have been, not the forms originally in the gathering, but those evidently derived from the water. Just at present, while we may-nay, perhaps must, admit that, up to a certain limit, diatoms, like the rotifers, may be dried, with power of revivification or reproduction, there is yet lacking sufficient evidence that this drying may extend over a series of years.

Parasites on a Diatom.

M. Guimard, while observing a gathering of diatoms, mostly Pinnularieæ, saw great numbers of them covered by small bodies of a yellowish-brown color, and moving with great rapidity. With a No. 5 of Nachet, they were seen to have a rectangular body, and contained in their interior a yellowish-brown matter, with globules of a deeper color, and resembling the ordinary endochrome of the diatoms; at each of the four angles was a long hyaline arm, of great mobility. Seen in profile, the body presented the form of an elongated oval (Bulletin de la Société Belge de Microscopie, vol. iv., p. 304).

Diatoms in Colored Liquids.

Professor H. L. Smith states that the communication which exists between the internal protoplasmic substance and the exterior does not take place along the sutures of the connectives, but in Navicula (properly so called) it exists along the raphé, or median line of the valves, and in Surirella and Nitzschia along the edges of the wings or carinæ. The absorption of the indigo, when the diatoms have been left for some days in liquid charged with this substance, is quite apparent, and principally at the ends of the median line, near the central nodule. Something similar was seen by Ehrenberg. In a field blue with indigo, the little particles can be seen running along the median line of a large Navicula (Pinnularia) on that half of the valve which is in the direction of the forward motion of the diatom; these particles accumulate at the end of the raphé, near the central nodule, where, in the large Pinnularieæ, a minute dot may be discerned, forming there a ball, which rotates precisely as though encountering a little stream of liquid issuing at this point. When the motion of the diatom is reversed, the particles traverse along the raphe of the other half of the valve to the centre, forming there a ball as before; these balls, after acquiring a certain size, are ruptured, and the particles stream off precisely as though moved by the cilia of a rotifer. There appears to be a gelatinous external hyaline envelope, the presence of which is not only demonstrated by the indigo particles, but by its becoming rapidly colored or stained by a weak solution of fuchsine (Bulletin de la Société Belge de Microscopie, Nov., 1877).

Isthmia Nervosa: a Study of its Modes of Growth and Reproduction.

Two very interesting papers upon this subject have been published in the May and June numbers of the American Journal of Microscopy, by the Hon. J. D. Cox, United States Senator, and they show how much can be accomplished by patient working and study of even imperfect materials. To study growth and reproduction one would suppose that living forms would be necessary; yet Senator Cox has arrived at many facts quite valuable by using only the dried or pre

pared material. A study of living forms would have shown, however, that the cushion, or gelatinous stipes, by which the frustules of the Isthmia are attached, and which constitutes in another form the stalks of Gomphonemea and Cocconemeæ, is in fact a closed gelatinous tube, out of which the diatom is constantly slipping. When the tube is not closed we have the fronds of Schizonemec and Colletonemeæ. All the diatoms secrete a more or less gelatinous sheath, over the whole surface of the frustule; it is not exuded at one end. What Mr. Cox calls the earlier view, viz., that the sporangial frustule becomes "the parent frustule of a new and vigorous generation, by recommencing the cycle of self-division," is not the earlier view, but is the later, accepted by all who have studied this subject in recent times, excepting perhaps Dr. Wallich, whose article, alluded to by Senator Cox, has many misjudgments and wrong statements. Thwaites himself did not express an opinion clearly. W. Smith, his intimate friend and the well-known British authority, in his classical work, supposes the cell-contents of the sporangium to break up and form broods of small individuals. Rabenhorst has even figured something of this kind in Melosira, and this was Kutzing's view in a general way. There is not a shadow of doubt that the opinion expressed by Senator Cox is the correct one. It has been advocated by Mr. Carter and others, and especially by Professor H. L. Smith (see the Lens, vol. i., p. 73), who has not merely observed the conjugation in some fifty genera, but has kept the sporangial frustules living until the self-division has been completed.

TISSUE-STAINING, BLOOD, ETC.

Structure of the Colored Blood-Corpuscles.

Dr. H. D. Schmidt, of New Orleans, states that the colored blood-corpuscles of the Amphiuma represent organic cells consisting of homogeneous protoplasm surrounding a nucleus, that part of the protoplasm forming the outer surface being of greater density than the rest, and so a membranous layer is formed, and may be seen in the form of a clear, narrow border of a greenish tint, and by the action of reagents it assumes the appearance of a distinct cell-wall. The coloring matter (hæmoglobin) of the blood-corpuscle does not seem

to be chemically united with the protoplasm, and it escapes readily, even by the action of very weak reagents. The nucleus represents an oval vesicle containing most probably a more or less dense liquid, with a number of larger and smaller granules. These first expand and then dissolve in water, increasing the volume of the whole contents and expanding the walls of the nucleus. The colored corpuscles of the frog resemble in form, as also in chemical and physical properties, those of the Amphiuma, but are less than half their size; when they are treated with water the coloring matter gradually disappears, but their outline is still visible, appearing in the form of a delicate double contour, which is the membranous layer of the corpuscle. The examination of the colored blood-corpuscles of man and the other mammalia is more difficult, in consequence of their smaller size. Those of man represent minute bi-concave disks with rounded margins, and a diameter of about mm. In a state of rest the outline is perfectly round; but when this outline is most distinctly in focus, the centre to about the extent of one third the whole diameter appears light. Between this and the bright margin is a varying shade caused by the form of the corpuscle. No trace of a membrane or a membranous layer can be discovered in the fresh blood-corpuscle of man. In the paper is a full discussion of the various changes in form and appearance of the blood-corpuscles due to external causes, and especially in connection with varying temperatures; also to the manifestation of spontaneous motion, due, as is stated, to living protoplasm, so that they have an inherent power of contracting and again resuming their original form. The changes in form, which increase rapidly in proportion to the length of time after removal from the living tissue seem to be the result of the last vital actions of the blood-corpuscle, and portend its death. Dr. Schmidt concludes that the function of the colored blood-corpuscles is at least partly secretory; he considers them as true glandular cells, engaged in appropriating certain materials from the plasm of the blood, in order to transform them into other bodies by virtue of their secretory power, and finally to return them to that fluid, in the condition required for the subservience of other purposes, such as the preservation of the normal constitution of the blood, as well as the nutrition of the vari

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