Dimorphism.

There are several cases of dimorphism known among grasshoppers-viz., two sets of individuals in the same species, which have been, or are liable to be, mistaken for different species. In the species allied to the common Rocky Mountain locust and the Eastern red-legged locust, Mr. Scudder states that there are ten or twelve species of these locusts, mostly occurring in the Mississippi valley, in which there are two sets of individuals-one with short and the other with long wings. In one instance three varieties occur, which are with little doubt to be referred to one species. The dimorphic forms of any one species are found at the same stations and cannot be considered racial.

Protection, Resemblance, and Coloration.

In an elaborate paper on the coloring matters of various marine animals, Mr. Moseley, late naturalist of the Challenger Exploring Expedition, calls attention to the coloring matters of deep-sea animals. Very little, if any, light, he says, can penetrate from the surface of the sea to depths such as 1000 or 2000 fathoms, and he believes that experiment has shown that little or no effect is produced on sensitized paper at the moderate depth of 60 fathoms. It is probably, as far as solar light is concerned, absolutely dark at depths of 1000 fathoms and upwards, and the fact that two blind decapod Crustacea occurred in from 450 to 490 fathoms seems to indicate a condition of extreme darkness at much less depths. Nevertheless, other animals living in very deep water have enormously enlarged eyes, and hence some light must exist. Professor Wyville Thomson and Dr. Carpenter have suggested that phosphorescent animals form the source of light in the deep sea. Mr. Moseley adopts this view, which seems to us, however, to be far-fetched, and adds that "the deep sea must be lighted here and there by greater or smaller patches of luminous Alcyonarians, with wide intervals, probably, of total darkness intervening. Very possibly the animals with eyes congregate around these sources of light." "No doubt," says Mr. Moseley, "in many cases the coloring of the deepsea animals, as in the case of the purple Holothurian, is useless and only an example of persistence. The madder color

ing of some of the soft parts of the corals may be in like case, but possibly useful for attraction of prey, being visible by the phosphorescent light. The same coloring matters exist in deep-sea animals which are found in shallow-water forms. Polyperythrin is found abundantly in surface-swimming Rhizostoma and in deep-sea Corals and Actinice. Autedonin occurs in a shallow-water (9 fathoms) Antedon at Cape York, and in a Holothurian found in 1975 fathoms near the Antarctic Sea. No doubt in many instances in the case of deep-sea possessors of these substances, the pigments, from being in the dark, never exercise their peculiar complex action on light during the whole life of the animal, but remain in darkness, never showing their color, as does Hæmoglobin in so many animals.

An essay on the colors of Animals and Plants, by Mr. Alfred R. Wallace, gives a general account of the more recent discoveries in this field of study. He believes "that neither the general influence of solar light and heat nor the special action of variously tinted rays is adequate cause for the wonderful variety, intensity, and complexity of the colors. that everywhere meet us in the animal and vegetable world." He groups them as follows:

Animals

1. Protective colors.

2. Warning colors. 6. Of defenceless creatures, mimicking a. a. Of creatures specially protected.

3. Sexual colors.

4. Typical colors.

Plants ....5. Attractive colors.

In a recent essay on the colors of British Caterpillars, Sir John Lubbock confirms the statements of several European naturalists, who have indicated that, as a general rule, caterpillars which are dull-colored and have a smooth skin or are nocturnal in their habits are greedily eaten by birds. On the other hand, spiny and hairy caterpillars are spared, and are often brightly colored. Certain species-such as Deilephila euphorbia, Abraxas grossulariata, and Zygana filipendula-are distasteful to birds; and in these cases brilliant coloring serves as a warning and, consequently, as a protection. Lastly, there are a few species-such as Charocampa elpenor and C. porcellus-which appear to frighten birds by their resemblance to small reptiles-a resemblance singularly heightened by the curious eye-like spots on the thorax.

Lubbock has studied this matter from a statistical standpoint, and finds that out of eighty-eight spiny and hairy species tabulated, only one is green (L. sybilla), while a very great majority of the black and brown caterpillars, as well as those more or less marked with blue and red, are either hairy or spiny, or have some special protection. His results confirm, in a remarkable manner, he thinks, the conclusions previously arrived at by the naturalists he names.

These

An interesting case of natural selection is described by Mr. S. F. Clarke in the American Naturalist. The writer obtained a large number of eggs of a salamander (probably Amblystoma opacum). They were hatched in due season, and then began, for want of proper food, to develop cannibalistic tendencies and to eat off one another's gills. It was discovered that among the many there were a few which, though they came from the same parents and were subjected to the same conditions while in the egg, were yet gifted with greater vigor and energy than most of their brothers and sisters. These few stronger ones ate off the gills of many of the weaker ones, and, at the same time, were enabled to protect their own from mutilation or destruction. favorable conditions-the large supply of food and the better aeration of the blood-soon began to show their influence upon the growth of the individuals thus favored. Within a week or ten days from the escape from the egg these favored few were fifty per cent. larger than their weaker comrades who were born upon the same day. "Their mouths had by this time increased so much in size that they were no longer satisfied with nibbling off the gills of their brethren, but now began to swallow them bodily. This great increase in the supply of food soon produced a marked effect upon those who were thus supplied; so that in ten days from the time that they began to feed in this way they were from ten to twelve times the length and bulk of those upon whom they were feeding. Developing at this rapid rate, they arrived at the stage when the gills are resorbed and the abranchiate form leaves the water for the marshy land or old, damp log, where it usually makes its home, and where it would find a supply of more natural food material. Here, then, was a very interesting case of natural selection by survival of the fittest: all the weaker individuals being

destroyed, and actually aiding the stronger ones by serving them as food until they could pass through their changes and escape to other regions where food was more abundant." A case of mimetic coloring in tadpoles is recorded by Sarah P. Monks in the American Naturalist for October. She finds that the tails of the tadpoles resemble the submerged lower leaves of a plant, Ludovidgia palustris, in color, width, and shape. The resemblance in color was so striking that a friend, who was not on the lookout for analogies, mistook a leaf for a tadpole.

Mr. Darwin has referred to two species of Orthoptera, allied to Pterochroza illustrata and P. ocellata, remarkable for their perfect imitation of dead leaves, which was carried out in the venation of the wings, even to microscopic details, as compared with the ribs and veining of leaves.

A number of instances of protection resemblance are given by Mr. Meldola, in the Annals and Magazine of Natural History. Among others is the case of an Indian Mantis, which resembles a flower.

General Embryology.

Recent observers-such as Bütschli, E. Van Beneden, Fol, Hertwig, Strasburger, and Calberla-have thrown a great deal of light on the phenomena of the maturation and impregnation of the egg. Their conclusions have been summarized as follows by Mr. F. M. Balfour, the eminent English embryologist. In what may probably be regarded as a normal case, the following series of events accompanies the maturation and impregnation of an egg: (1) Transportation of the germinal vesicle to surface of the egg; (2) absorption of the membrane of the germinal vesicle and metamorphosis of the germinal spot; (3) assumption of a spindle character by the remains of the germinal vesicle, these remains being probably largely formed from the germinal spot; (4) entrance of one end of the spindle into a protoplasmic prominence at the surface of the egg; (5) division of the spindle into two halves, one remaining in the egg, the other in the prominence; the prominence becomes at the same time nearly constricted off from the egg as a polar cell; (6) formation of a second polar cell in the same manner as the first, part of the spindle still remaining in the egg; (7) conversion of the

part of the spindle remaining in the egg after the formation of the second polar cell into a nucleus-the female pronucleus; (8) transportation of the female pronucleus towards the centre of the egg; (9) entrance of one spermatozoon into the egg; (10) conversion of the head of the spermatozoon into a nucleus-the male pronucleus; (11) appearance of radial striæ round the male pronucleus, which gradually travels towards the female pronucleus; (12) fusion of male and female pronuclei to form the first segmentation nucleus.

It may be remembered that Dr. E. L. Sturtevant contributed to the American Naturalist for August a note on the development of unfertilized eggs in the body of the female pickerel. In the October number of the same journal Dr. W. K. Brooks gives the history of previously published cases of a similar nature, with the authorities. Dr. Burnett saw in eggs of the codfish before they were expelled from the ovaries, and therefore before impregnation, phenomena indicating that the segmentation of the yolk had already begun. Agassiz declared that eggs in various early stages of development may be found in the ovaries of the cod, whiting, and hake. Bischoff states that a few unfertilized eggs of the European frog were found to go through the early stages of development, and this has been confirmed by another French writer. Bischoff found eggs in various stages of segmentation in the ovaries of a virgin sow, and Hensen observed the same in the rabbit. Oellacher found that eggs laid by virgin hens undergo segmentation and form a blastoderm while in the oviduct, and he regards this as a normal process. Vogt says the unfertilized eggs of Firola, a mollusk, undergo segmentation, and Quatrefages records the same occurrence in Unio. Dr. Brooks concludes that "the egg has in itself the power to form a new individual, although this power is never perfectly, and usually not at all, shown until development is excited by the influence of the spermatic filaments of the male."

INVERTEBRATES.

Protozoa.

Professor Leidy's recent investigations have led him to suspect that the species of fresh-water Rhizopods are cos