the species by written characters or descriptions is beyond my powers. But no one has ever seen so many of the type-specimens of the species as I have, nor given more time to the systematic study of these genera.

*

* *

"It is noticeable that the herbarium of Nees von Esenbeck for Aster is not referred to. I cannot ascertain what has become of it. But the types of several of his species, or specimens named by him, have been met with in other herbaria, especially in that of Lindley, and that of Schultz, Bip., the latter now a part of the large collection of Dr. Cosson. As to Asters, I do not here attempt anything beyond a report of the main results of the study of certain principal herbaria; and I leave the high northern and far western species out of the present view."

ZOOLOGY.

HABITS OF FRESH-WATER CRUSTACEA.-No one branch of biological study is now bringing forth more interesting and every way useful results than embryology. Throwing light as it does, not only on questions of classification and theoretical biology, but also on the application of such theories to practical life, this new science may be termed at once the root and most typical fruit of a revolutionized biology. No other science furnishes a better illustration of the value of minute, accurate study of the most common and apparently insignificant facts. Sets of isolated facts evolved by conscientious study of different men spring suddenly into line when once the clue is found, and the result may be a new law which renders all these facts eloquent. To the systematist the merely external study of life histories is of greatest value as a check against redundancy in classification, and furnishes the only reliable method, among lower forms at least, of setting the bounds of species.

Many eminent monographers have been obliged to considerably augment the nomenclature of their specialty with names which, later, have proved to apply simply to larval or immature forms, on account of the impossibility of following the whole life history of each individual.

To confine ourselves to the class Crustacea, many instances of this sort could be recounted. The best known is perhaps that of the common Cyclops which in the earlier days of carcinology enjoyed as many as three names between its exclusion from the egg and maturity. The discovery of the earlier stages in the life of Cyclops opened a new vista in the whole subject, and now we recognize a "Nauplius stage" in the life-history of nearly every

crustacean.

It has been more recently discovered that similar opportunities for error are afforded by the difficulty of distinguishing the ultimate stage in an animal's life. It has been shown that the functions of reproduction are anomalous in the lower animals. Espe

cially is this true in Crustacea, in so much that their condition affords no sufficient evidence that the sexually mature animal is in its historically perfect form. The enthusiasm elicited by the discovery that certain amphibians, under some circumstances, reproduce during a larval stage, was almost unparalleled, but I believe it demonstrable that, not only species, but families of lower Crustacea are normally sexually mature in a stage preceding actual maturity.

We most naturally turn to the order Branchiopoda for a test, since the most remarkable cases on record of heterogeneous reproduction have recently been read in their history. We need only mention the parthenogenetic summer brood of Daphnia,' and the case of heterogenesis discovered by G. O. Sars in Leptodora, in which Sars concludes that L. hyalina has both "dimorphous development and alternation of generations." Nor are we disappointed in looking among the Cladocera for examples of heterogenesis. During the winter semester of 1881-82, at Leipzig University, we had the opportunity of studying the development of Daphnia magna (=schäfferi), and among other interesting facts the following were elicited:

The development proceeds in very much the way described for Moina by Grobben.3 The secondary or swimming antennæ have an evident palpus in the nauplius stage, however, which makes the parallel complete between Copepod and Branchipod Crusta

The heart and circulatory system apparently is formed differently from the method given by Grobben. I may be permitted to say in this connection, that the circulatory system is much more complicated than hitherto described, and seems to originate about a mass of deutoplasm which surrounds the intestinal canal in the embryo, and which is a remainder of the food-yolk, Nährungsdotter," of the egg. The embryo, in a comparatively early age, begins to differentiate the walls of the valves, which first appear as a fold over the maxillary region near the position. occupied by the heart, and extends gradually backwards in a thick fold of turgid cells between which fluid flows. Quite remarkable is it that from the dorsal region a process extends, growing much more rapidly than the lateral portion till it reaches the membrane of the egg, when it curves downward and forwards till it reaches a position nearly half way from the extremity of the abdomen to the maxiliæ. The method of growth of this tail-like appendage of the shell is obscure, but it seems to stand in close relation to the formation of the brood

1 See J. Lubbock; Phil. Trans., Vol. 147, p. 98.

Cfr. R. Leuckart: Archiv, f. Naturg., XXXI, and

v. Siebold: Wahre Parthenogenesis bei Schmetterlingen und Bienen.

2 G. O. Sars: Om en dimorph Udvikling samt Generations vexel hos Leptodora, 1873.

Die Entwicklungeschichte der Moina rectirostris, von Dr. Carl Grobben. Vienna,

cavity, and is the result of a secondary folding of the common shell envelop. At the close of the development in the egg, this "tail" lies between the valves of the shell, curved beneath like the tail of a frightened dog, although the frequent motions of the post-abdomen are not a little hindered thereby.

On its escape from the egg, the animal swims freely, and soon kicks this pliant appendage backward and upward till it assumes a direction parallel to the long axis of the body, and then very soon its unequal growth causes this tail to be somewhat elevated. The appendage probably serves as a support for the cast off skin in the molt, so that it cannot fall down upon the post-abdomen and then be broken off before that portion of the shell forming the inner covering of the brood cavity can be successfully molted -a danger especially incident to long forms with narrow brood cavities, and to young animals in which the shell is tender. (It may be for this reason that males, in which the part corresponding to the brood cavity is very narrow, and young females, have this spine, while adult females do not, for, as is well known, the males of all this section of the genus are spined through life.) Successive moltings increase the size of the animal, but the spine remains and increases correspondingly, giving the animal a very different appearance from the parent, which was not only of an entirely different form but totally without the spine.

Finally the young female produces eggs parthenogenetically, and is, therefore, according to our customary notions, an adult. We have here, therefore, a case of heterogenesis. Under circumstances where food is not sufficiently abundant, it seems certain that the above-mentioned state is the final one, and that the animal does not reach that condition which we name Daphnia magna, but remains in a stage which has received a different specific

name.

The same process has since been observed in the case of Daphnia pulex, in Minnesota. Some of the so-called varieties are but ageforms. There is in each species what may be called a post-imago form, which is only assumed under favoring conditions. Without going into the synonymy of this genus, which will bear a revision in view of this and similar facts, we may safely say that in the Daphnidæ we find heterogenesis almost a rule, at least in the genus Daphnia. We may add that every possible provision for the reproduction of these animals seems to be provided. (1) They are very prolific; (2) reproduce both sexually and parthenogenetically; (3) resist great extremes of temperature; (4) accommodate themselves to great alterations in the purity of the water; (5) the winter eggs are provided with a horny covering or ephippium, which permits them to be dried in a mass of mud or frozen in a cake of ice without destroying their vitality; (6)

1 See Birge, Notes on Cladocera, Madison, Plate II, Fig. 6.

during mild winters both summer and winter eggs are produced, and the successive broods of young after producing agamic young, throw off an ephippium so that the pool is filled with eggs which are calculated to stand any vicissitude. Thus it happens that after a pond has been dried for a long time the first warm shower quickens in it swarming life. The above facts are more significant when we remember that the Cladocera are above all others among Crustacea, the most useful as purifying agencies. The greater number subsist entirely upon vegetable matter, and the only means they have of collecting it is by causing a current of water containing such minute particles as may exist in it to pass between the rotating jaws, though, perhaps, in some cases the labrum is sufficiently prehensile to grasp somewhat larger food. Certain it is, however, that these same minute animals form an indispensable agent in the economy of nature, purifying all our stagnant pools of the decaying vegetation floating therein. One who had given no attention to the number of these creatures would undoubtedly be surprised on carefully examining a given quantity of water from the nearest lake. Here are some figures. In a quart of water taken by dipping from a lake near Minneapolis, the following were counted:

etc., all visible to the unassisted eye.-C. L. Herrick.

ON THE HABITS OF CRYPTOBRANCHUS.'-Living examples of this Japanese salamander have rarely been brought to this country, and the following observations may be worth recording even if they merely confirm those of Hyrtl, Van der Hoeven and others, whose works I have not yet had an opportunity to consult.

This specimen is about seventy-five centimeters (21⁄2 ft.) long, and was obtained for Cornell University through Professor H. A. Ward, who brought it by hand from Japan.

It is very sluggish, remaining quiet for hours in water, excepting for the respiratory movements presently to be described. Nevertheless it can display considerable activity, and upon one occasion escaped from a common wash-tub which was about thirty centimeters (1 ft.) deep. Out of water it appears uncomfortable, and crawls first in one direction and then in another,

1 Read at the Montreal Meeting of Amer. Association for Advancement Science, August, 1882.

with frequent stoppages. It evidently seeks shelter from the sun, but gives no sign of discrimination between objects, walking against dogs and cats and people as readily as against wood and stone. The trunk is never lifted from the ground, and the compressed tail rests on one side, but the head and neck are sometimes raised.

The respiratory actions in deep water I have not accurately observed, but in shallow water, just covering it, the nostrils are raised above the surface at frequent intervals, a slight hissing sound is heard, and after the nostrils are again carried below the surface, a few bubbles of air escape therefrom and there are muscular movements about the neck. During an hour, in freshly changed water, these respiratory actions occurred at intervals varying from half a minute to twelve minutes, but usually the time was from two to four minutes.

No notice was taken of raw or cooked beef or fish, either floating at the surface, lying at the bottom or suspended just above the water.

But if bits of food are dropped close to the mouth or allowed to slide over the top of the head, or held at the lips, they are readily snapped up and swallowed, if not too large. After a time the head was moved slowly toward meat held about one centimeter from the lips, but I could not determine whether sight or smell were the sense concerned. Neither have I ascertained the function of the tubercles.

This specimen has now eaten the following articles: Beef heart, raw and boiled; blue-fish, raw and broiled; hard boiled white of egg, canned roast beef, raw lamb's heart, liver, diaphragm, thymus and lung, baked maccaroni. Evidently there is no difficulty in keeping the animal alive.

I hope to make careful observations of Cryptobranchus in comparison with Menopoma and Menobranchus.-B. G. Wilder, Ithaca, N. Y

MAMMALS OF NEW GUINEA.-The Annals of the Museum of Natural History, Genoa, for 1880-81, contain a list of fifty-seven species of mammals collected in New Guinea by L. M. D'Albertis and A. A. Bruijn, illustrated with fourteen plates of new species. The work of identification and description has been performed by Dr. Peters, director of the Berlin Museum, and G. Doria, director of that of Genoa.

In their introduction these gentlemen state that the Australian element in the New Guinea fauna is continually on the increase, as evidenced by the late discovery in that island of the genera Tachyglossus, Dasyurus and Dromicia. Thirty species of marsupials, forming almost the half of the known mammals of Papua, have been found, and, although almost all the species are peculiar, The habits of this species are described by Duméril and Bibron, Herpetologie Generale, IX, 1854, p. 165.

2 Annali del Museo Civico di Storia Naturale di Genova, Vol. xvi, 1880-81.