SCIENCE. 



[N. S. Vol. XI. No. 286. 



believed to furnish the means for unravel- 

 ing animal genealogies. 



All three of these lines of research have 

 been pursued (from the phylogenetic stand- 

 point) with great enthusiasm since 1859, 

 and they are still being pursued : the results 

 have, however, fallen far short of meeting 

 anticipations. From the paleontological 

 side it was evident from the first that many 

 animals had left no recognizable fossil re- 

 mains. In other cases the remains were so 

 imperfect, so difficult of access and so few 

 that nothing like a complete series could be 

 hoped for. Paleontology has accomplished 

 a great deal. Where it is available, it is 

 without doubt the safest guide, perhaps the 

 only safe guide in phylogenetic speculation. 

 On the other hand it has not, and in the 

 nature of its materials cannot lead to a re- 

 alization of the zoologists' dream of a phy- 

 logenetic millenium. 



Comparative anatomy has been to a con- 

 siderable extent neglected during the past 

 thirty years. Among the invertebrates, 

 where the research could be carried on by 

 the rapid methods of modern microscopic 

 technique there has beeu more work, than 

 among the larger vertebrates where it is 

 necessary to use the tedious method of dis- 

 section. Among the anatomical research 

 of the last quarter of a century there is a 

 noticeable dearth of monographic work. In 

 the earlier part of the century anatomists 

 were not so much concerned with the dis- 

 covery of relationships, they were content 

 to work long on single animals, and there 

 were thus produced anatomical monographs 

 which have not since been suj'passed in 

 quality. With the advent of Darwinism 

 came a feverish haste to detect relationships, 

 and this resulted in a desire to compare 

 large numbers of animals with one another. 

 The time required to study the whole struc- 

 ture of a large series of animals was too 

 great for the life time of one man. Much 

 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 comparative anatomy of 

 organs. 



A second characteristic of the compara- 

 tive anatomy of this period has been its 

 great reliance upon embryology. Its facts 

 have been too often 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 apex. 



Embryology was, however, the guiding star 

 of the post-Darwinian workers. It seemed 

 to offer by far the easiest and quickest solu- 

 tions of their problems. It soon developed 

 a technique of great intricacy and of great 

 accuracy, and it came to offer easy con- 

 quests to the ambitious investigator. Its 

 faintest hints at relationship were accepted 

 as of the utmost importance and were given 

 the deepest meaning. Scarcely any zoolog- 

 ical work was complete without its embry- 

 ological 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 ancestoral fea- 

 tures were always more or less modified 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 adapt itself to 

 its own very difierent conditions. The de- 

 velopment 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 

 (csenogenetic factors). The record was 

 thus said to be falsified and to pick out the 

 true from the false became the difficult task 

 of the embryologist. This was a task re- 

 quiring great judgment and one concerning 

 which individual observers were likely to 

 differ greatly. If an observer started out 

 with a certain theorj' as to the ancestral 



