26 MICHIGAN ACADEMY OF SCIENCE. 



technique there has been more work, than airfong the larger vertebrates 

 where it is necessary to use the tedious method of dissection. Among 

 the anatomical research of the last quarter of a century there is a 

 noticeable dearth of niouiKiraphlc work. In the earlier part of the 

 century anatomists were not so much concerned with the discovery of 

 relationships, they were content to work long on single animals, and 

 there were thus produced anatomical monographs which have not 

 since lieen surpassed in quality. With the advent of Darwinism came a 

 feverish haste to detect rehitionships, and this resulted in a desire to 

 compare large numbers of animals with one another. The time required 

 to study the whole structure of a large series of animals was too great 

 for the lif(^ time of one man. ^Nluch could, however, be accomplished 

 by the comparison of a single organ through a large series of animals — 

 and so the comparative anatomy of animals (monographic work) gave 

 place to the coni})arative anatomy of organs. 



A second characteristic of the comparative anatomy of this period 

 has been its great reliance upon embryology. Its facts have been too 

 ofteh distorted to make them fit with the results of embryological work, 

 and thus what should be the base of the pyramid has been made its 

 a{)ex. 



Embryology was, however, the guiding star of the post-Darwinian 

 workers. It seemed to offer by far the easiest and quickest solution of 

 their problems. It soon developed a technique of great intricacy and 

 of great accuracy, and it came to offer easy conquests to the ambitious 

 investigator. Its faintest hints at relationship were accepted as of 

 the utmost importance and were given the deepest meaning. Scarcely 

 any zoological work was complete without its embryological side. But 

 it soon became evident that the development of an animal could not be 

 construed as a simple repetition of its ancestral history. The ancestral 

 features were always more or less modilied by features impressed upon 

 the developing animal by its surroundings. The embryo was, so to 

 speak, burdened by a double task. It not only repeated the history of 

 its ancestor, but it had also to ada]tt itself to its own very different 

 conditions. The development thus came to be considered as made up 

 of two factors — those that were ancestral (phylogenetic) and those that 

 were acquired by the embryo and peculiar to it (ctenogenetic factors.) 

 The record was thus said to be falsified and to ]>ick out the true from 

 the false became the difiicult task of the embryologist. This was a 

 task requiring great judgment and one concerning which individual 

 observers were likely to differ greatly. If an observer started with 

 a certain theory as to the ancestral histoi-y of an animal, all those 

 factors in its development which did not accord with the theory, were 

 apt to seem to him to be falsifications of the record. Another observer 

 with the same facts before him. but woi-kiug on a different theory, 

 would discover that many of these so called falsifications were really 

 ancestral features. 



Anotlun- factor which has hampered embryology as a phylogenetic 

 discipline has been the too frequent limitation of the investigation to 

 a single organ. It is easier to investigate a single organ through a 

 series of embryos than to investigate the entire structure of all the 

 members of the scmmcs. \A'e are able to judge correctly of the character 

 of a man only when we know all the elements that make it up. And so 



