of my vases have quadrangular inscriptions, of which I have not yet had time to make photographs. Lately the Globus published accounts of several of my smaller expeditions, accompanied by some twenty photographical illustrations which you may perhaps see in the Globus, Nos. 16 and 18, for 1895. ·

Some days ago, an earthen vessel, full of little implements of worked stone, was found at a hacienda near Ticul. I have been promised the specimens, and will communicate with you in case they turn out to be of interest. From the cave of Loltun, I have several very good photographs Lol Bejuco, the Haytian name for hanging plants (the name Vana is not used in Mexico); tun = stone; Loltun = stalactites hanging stones or stones like hanging plants.

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I shall be glad to publish, from time to time, in American scientific or popular journals, small articles describing my Yucateckan discoveries, and when my present work of enlarging photographic negatives is finished, shall be ready to prepare for you a series of accounts of my work, accompanied by the necessary celluloid positives from which it is easy to make reversed negatives for the photolithographic process. Next year I shall return to the States of Tabasco and Chiapas, where I have still to explore several entirely unknown ruins hidden in the wilderness occupied by the Lacandones Indians.

Ticul, November 20, 1895.

-THEOBERT Maler.

SCIENTIFIC NEWS.

The Biological Station of the University of Illinois is first to issue its circular for the summer of 1896. The station staff is composed of Professor S. A. Forbes, Director; Dr. C. A. Kofoid, Superintendent; Frank Smith and Adolph Hempell, Zoological Assistants; Dr. A. W. Palmer and C. V. Millar, Chemists; C. A. Hart, Entomologist and B. M. Duggar, Botanist. The station is situated upon the Illinois River near Havana, Ill., and is equipped with every facility for collection and study. There is a floating laboratory sixty feet long and twenty wide, a steam launch, licensed to carry 17 persons, and all the necessary supplies of tables, microscopes, aquaria, nets, chemicals, etc., as well as a specially selected library. As there are accommodations for only 16 in addition to the station staff, applications for the coming summer will be received only from those who have had sufficient experience to place them beyond the need of continuous supervision in their investigations, and, other things being equal, instructors in biology in colleges and high schools will receive the preference. The station will be open

during June, July and August. An incidental fee of $5.00 a month will be charged, and no application for tables should be made for less than two weeks. Board and rooms can be had in Havana at from $4.00 to $5.00 a week. All applications should be addressed to the Director, Professor S. A. Forbes, Urbana, Ill.

The announcement is made that Professor Marshall Ward has been elected to the Chair of Botany in the University of Cambridge, England, to fill the vacancy occasioned by the death (July 22, 1895) of the venerable Professor C. C. Babington.

The University of Cambridge receives the botanical collection of the late Professor Babington.

Mr. F. B. Stead, of Cambridge, England, has been appointed to carry on the investigations of the fisheries at the Plymouth Laboratory, and Mr. T. V. Hodgson as Director's Assistant in the same institution.

After an interregnum of several years, Washburn University, Topeka, Kan., has appointed Dr. G. P. Grimsby, of Columbus, Ohio, to the Chair of Geology and Natural History.

Drs. Walter B. Rankin and C. F. W. McClure, of Princeton, have been advanced to Professorships in Biology in the College of New Jersey.

The Government of the Cape of Good Hope has recently established a geological commission to carry on a survey of that region.

Dr. R. H. True has been appointed Instructor in Pharmacognostical Botany in the University of Wisconsin.

Dr. W. S. Strong, of Colorado, is called to the Chair of Geology in Bates College, Lewiston, Maine.

Bernard H. Woodward has been appointed Curator of the Museum at Perth, W. Australia.

Dr. R. Metzner has been elected Professor of Physiology in the University of Barcelona.

Dr. Dalle-Torre is now Assistant Professor of Zoology in the University of Innsbruck.

Dr. Hans Lenk has been appointed Professor of Geology in Erlangen.

Dr. Ducleaux has been elected President of the Pasteur Institute.

It has long been known that animals develop according to two types, appearing in their younger stages, either as larvæ or as embryos. The larvæ lead a free life and must obtain their own food. Embryos, on the contrary, do not lead a free life and are nourished by the yolk accumulated in the parent ovum. There is, of course, no absolute demarcation between the two classes; nevertheless, a general comparison between them establishes several conclusions which throw valuable light upon some recent biological hypothesis.

First of all, it must be remarked that the larval development is primitive, and that the embryonic development has been evolved later. Geologists are able to present two principal supports for this assertion: 1. In the lower animals we encounter only larvæ, never embryos; sponges, colenterates, echinoderms and worms, all pass through the early stages of * Read before the Amer. Soc. of Morphologists, December, 1893.

their ontogeny as larvæ. It would, therefore, be superfluous to linger for the defense of a view which is already accepted by all biologists. 2. The embryonic development depends on the presence of yolk. Now we have learned that the yolk has developed very gradually and in all the lower animals appears only in small quantities. It was not until the increase of yolk material had become enormous, as, for example, in the meroblastic vertebrates, that we find the development completely embryonic in type. With the increase of the yolk comes the gradual transition from larval to embryonic development. Since the embryo is dependent on the yolk, and since the yolk exists only in the higher forms in sufficient quantity, it follows that fully typical embryos can occur exclusively in the higher (later developed) animal types.

The fact that larvæ represent the primitive forms of development, obliges us to conclude that the correctnesss of Weismann's theory of the continuity of germ plasm can be tested better in larvæ than in embryos, since in embryos the relations have undergone profound modifications by secondary changes, which in this connection might easily deceive us.

I do not venture to assert that I know what the present form of Weismann's continuity theory may be; I hold, however, the exact form of this much discussed theory to be nonessential, because, according to my conviction, the theory can in no form be brought into agreement with our present knowledge. Nussbaum founded the theory, and opened the way along which we certainly hope to make great advance. Let me acknowledge the great value and the strictly scientific character of Nussbaum's work; doing this not merely because I esteem it, but also because the unjust attempt has been made to diminish his claim. Nussbaum thought that the germ cells are direct decendents of the fertilized ovum, keeping the germinating power. while the rest of the cells developed from the egg are transformed into the tissue of the body. He brought forward several facts which could be interpreted in favor of his theory. By this theory the whole problem of her

9 M. Nussbaum, Zur Differenzierung des Geschlechts im Tirreich, Arch. f. Mikrosk. Anatomie, XVIII, 1--121, (1880).

edity and development was stated in an entirely new form. Since this publication of Nussbaum's we are seeking for the explanation of the germinating power, and the propagation of this power; formerly we sought for the causes of the inheritance of parental parts. The difference may be illustrated by the following example. Before Nussbaum we were ruled by Darwin's conception of Pangenesis, and we investigated accordingly for the agency by which the eye of the father reproduced itself in the child. Since Nussbaum we leave Pangenesis behind-it belongs henceforth to the past-and try to determine how the germinal substance behaves, and especially in what way it is perpetuated from the ovum through the following developmental stages, so that it is finally still present for the creation of the next generation. It is the conception of the continuity of the germinal substance which we prize so highly, and owe to Nussbaum.

Larvæ teach us that it cannot be special cells which affect this continuity. In fact, we find the organs of larval life fully differentiated before any sexual organs are recognizable, and indeed, in the majority of known larvæ we cannot recognize even the rudiments of the sexual glands. On the contrary, we find in larvæ unmistakably differentiated locomotive apparatus, such as cilia and often muscle fibres, a digestive canal, sensory organs, and, in many cases, also special excretory organs, and yet, only in a very few and exceptional cases can we distinguish the cells which belong to the future sexual glands. Thus, in regard to the primitive or larval type of development, we cannot say that the germ cells are constantly separated from the somatic cells during the segmentation of the ovum, but must rather draw precisely the opposite conclusion, namely, that the germ cells belong to the tissues which arise latest. We often meet many tissues in larvæ at a time when there is still no indication of germ cells. We find the same relations in embryos also, since in them the principal tissues become recognizable before germ cells are present. This fact was well established for vertebrates many years ago. It is characteristic of Weismann that he long defended the continuity of germ cells, in defiance of the facts. He has since