436 OCEANOGRAPHY, BIONOMICS, AND AQUICULTURE. 



investigate not merely the cellular anatomy of the body, but the anat- 

 omy of the cell — if, indeed, we are permitted to talk of " cell " at all, and 

 are not rather constrained to express our results in terms of u cytomi- 

 crosoines," " somacules," or " idiosomes," and to regard our morpholog- 

 ical unit, the cell, as a symbiotic community containing two colonies of 

 totally dissimilar organisms. (See Watase in " Wood's Holl Biological 

 Lectures," 1893.) To such cytological investigations may well be 

 applied Lord Macaulay's aphorism, "A point which yesterday was 

 invisible is its goal to-day, and will be its starting point to-morrow." 



Somewhat similar advances in" methods have led us from the life 

 histories studied of old to the new and fascinating science of embry- 

 ology. The elder Milne-Edwards and Yan Beneden knew that in their 

 life histories Ascidians produced tadpole-like young. Kowalevsky 

 (1866) showed that in their embryonic stages these Ascidian tadpoles 

 have the beginnings of their chief systems of organs formed in essen- 

 tially the same manner and from the same embryonic layers as in the 

 case of the frog's tadpole or any other typical young vertebrate; and 

 now we are not content with less than tracing what is called the "cell- 

 lineage" of such Ascidian embryos, so as to show the ancestry and 

 descendants, the traditions, peculiarities of, and influences at work 

 upon each of the embryonic cells — or areas of protoplasm — throughout 

 many complicated stages. And there is now opening up from this a 

 great new field of experimental and "mechanical" embryology, in which 

 we seek the clew to the explanation of particular processes and changes 

 by determining under what conditions they take place, and how they 

 are affected by altered conditions. We are brought face to face with 

 such curious problems as, Why does a frog's egg, in the two-celled stage, 

 of which one-half has been destroyed, develop into half an embryo when 

 it is kept with one (the black) surface uppermost, and into — not half an 

 embryo, but — a whole embryo of half the usual size if kept with the 

 other (the white) surface upward. Apparently, according to the con- 

 ditions of the experiment, we may get half embryos or whole embryos 

 of half size from one of the first two cells of the frog's egg. 1 



One of the most characteristic studies of the older field naturalists, 

 the observation of habits, has now become, under the influence of Dar- 

 winism, the "Bionomics" of the present day, the study of the relations 

 between habit and structure and environment — a most fascinating and 

 promising field of investigation, which may be confidently expected to 

 tell us much in the future in regard to the competition between species, 

 and the useful or indifferent nature of specific characters. 



Other distinct lines of zoological investigation, upon which I shall 

 not dwell, are geographical distribution and paleontology — subjects 

 in which the zoologist comes into contact with and may be of some 

 service to his fellow-workers in geology. And there still remains the 



•See Morgan, "Anat. x\nzeig./' 1895, X, Bd. p. 623, and recent papers by Roux, 

 Hertwig, Born, and O. Schultze. 



