260 



SCIENCE 



[N. S. Vol. LII. No. 1348 



unit, the species, is insecure owing to the dis- 

 covery of gradual changes. But this is a diffi- 

 culty which the paleontologist shares with the 

 neontologist. 



Let us consider another way in which the 

 time-concept has affected biology. 



EFFECT OF THE TIME-CONCEPT ON IDEAS OF 

 RELATIONSHIP 



Etienne Geoffroy-Saint Hilaire was the first 

 to compare the embryonic stages of certain ani- 

 mals with the adult stages of animals consid- 

 ered inferior. Through the more precise ob- 

 servations of Von Baer, Louis Agassiz, and 

 others, the idea grew until it was crystallized 

 by the poetic imagination of Haeckel in his 

 fundamental law of the reproduction of life — 

 ■namely, that every creature tends in the course 

 of its individual development to pass through 

 stages similar to those passed through in the 

 history of its race. This principle is of value 

 if applied with the necessary safeguards. If it 

 was ever brought into disrepute, it was owing 

 to the reckless enthusiasm of some embryolo- 

 gists, who unwarrantably extended the state- 

 ment to all shapes and structures observed in 

 the developing animal, such as those evoked 

 by special conditions of larval existence, some- 

 times forgetting that every conceivable an- 

 cestor must at least have been capable of earn- 

 ing its own livelihood. Or, again, they com- 

 pared the early stages of an individual with the 

 adult structure of its contemporaries instead 

 of with that of its predecessors in time. 

 Often, too, the searcher into the embryology 

 of creatures now living was forced to study 

 some form that really was highly specialized, 

 such as the unstalked Crinoid Antedon, and 

 he made matters worse by comparing its 

 larvaB with forms far too remote in time. All- 

 man, for instance, thought he saw in the de- 

 veloping Antedon a Cystid stage, and so the 

 Cystids were regarded as the ancestors of the 

 Crinoids; but we now find that stage more 

 closely paralleled in some Crinoids of Carbon- 

 iferous and Permian age, and we realize that 

 the Cystid structure is quite different. 



Such errors were due to the ignoring of time 

 relations or to lack of acquaintance with ex- 



tinct forms, and were beautifully illustrated 

 in those phylogenetic trees which, in the 

 'eighties, every dissector of a new or striking 

 animal thought it his duty to plant at the end 

 of his paper. The trees have withered, be- 

 cause they were not rooted in the past. 



A similar mistake was made by the paleon- 

 tologist who, happening on a new fossil, bla- 

 zoned it forth as a link between groups previ- 

 ously unconnected — and in too many cases 

 unconnected still. This action, natural and 

 even justifiable under the old purely descrip- 

 tive system, became fallacious when descent 

 was taken as the basis. In those days one 

 heard much of generalized types, especially 

 among the older fossils; animals were sup- 

 posed to combine the features of two or three 

 classes. This mode of thought is not quite ex- 

 tinct, for in the last American edition of Zit- 

 tel's " Paleontology " Sfephanocrinus is still 

 spoken of as a Crinoid related to the Blastoids, 

 if not also to the Cystids. Let it be clear that 

 these so-called " generalized " or " annectant " 

 types are not regarded by their expositors as 

 ancestral. Of course, a genus existing at a 

 certain period may give rise to two different 

 genera of a succeeding period, as possibly the 

 Devonian Calocrinus evolved into Aganco- 

 crinuSj with concave base, and into Dorycrinus, 

 with convex base, both Carboniferous genera. 

 But, to exemplify the kind of statement here 

 criticized, perhaps I may quote from another 

 distinguished writer of the present century: 



The new genus is a truly annectant form uniting 

 the MelocrinidBB and the Platyerinidse. 



Ifow the genus in question appeared, so far 

 as we know, rather late in the Lower Carbonif- 

 erous, whereas both Platyerinidse and Melo- 

 crinidae were already established in Middle 

 Silurian time. How is it possible that the 

 far later form should unite these two ancient 

 families^ Even a mesalliance is inconceivable. 

 In a word, to describe any such forms as 

 "annectant " is not merely to misinterpret 

 structure but to ignore time. 



As bold suggestions calling for subsequent 

 proof these speculations had their value, and 

 they may be forgiven in the neontologist, if 



