976 



SCIENCE. 



[N. S. Vol. XV. No. 390. 



chorology, according to the particular as- 

 pect of the subject under consideration. 

 On the other hand, the interests of all these 

 various sciences are slowly but surely con- 

 verging to a point which is not far from 

 the center of gravity of 'ethology.' This 

 is apparent in the 'types' and 'habitus' of 

 the systematist and morphologist, in the 

 conceptions of the ' individual,' in experi- 

 mental embryology and the study of 

 growth and regeneration, in the concep- 

 tions of 'adaptivity' among the 'neovital- 

 ists,' in the mystic zoology of a Maeter- 

 linck, in the theories of 'determinate 

 variations' and 'orthogenesis,' in recent 

 experimental work on the origin of muta- 

 tions, etc. In all this work there is appar- 

 ent a turning away from the 'mechanical' 

 and 'environmental,' a realization of the 

 prematureness and inadequacy of all 

 biological ' explanations ' couched in terms 

 of existent chemistry and physics, and an 

 appreciation of greater depth and mystery 

 in the life activities than had been pre- 

 viously conceded. 



So numerous are the signs of the time 

 that it requires little prophetic insight to 

 discern that we are on the eve of a 

 renascence in zoology. There have been 

 voices crying in the wilderness for many 

 years, and it may be well to hark back to 

 some of these and catch the full force of 

 their intention. First there was Goethe, 

 who glowed with the magnificence of the 

 problem : 



"Was ist doch ein Lebendiges fiir ein 

 kostliches, herrliches Ding! wie abge- 

 messen zu seinem Zustande, wie wahr, wie 

 seiend ! ' ' 



Then there was the father of develop- 

 mental science, Karl Ernst von Baer, who 

 began to doubt whether the field he had 

 himself cultivated with such success would 

 yield more than a small portion of the de- 

 sired harvest : 



"Wissen mochten wir ob das 20. Jahr- 

 hundert nicht, wenn man die Kunst das 

 Lehen im Lehen zu beobachten, wieder 

 gelernt hat, iiber die Selbstzufriedenheit 

 des 19. lacheln wird, mit der es glaubt, aus 

 dem Leichnam das Leben in seiner ganzen 

 Fiille erkennen zu konnen, fast vergessend, 

 dass mit dem bildenden Leben ein 

 handelndes innig verbunden ist, das dem 

 Messer und dem Mikroskop sieh entzieht." 



And among the latest there is Jules 

 Fabre, indefatigable observer and incom- 

 parable Avriter, who points to the old, sure 

 method of all science as the method of 

 ' ethology ' : 



"Large part faite a I'anatomie, precieuse 

 auxiliaire, que savons-nous de la bete? A 

 pen pres rein. Au lieu de gonfler avec ee 

 rien d 'abracadabrantes vessies, glanons des 

 fails bien observes, si humbles soient. ' ' 

 William Morton Wheeler. 



Austin, Texas, 

 May 17, 1902. 



THE LAW OF VON BAER. 

 BASED ON- SCHOLION V. 



The writings of von Baer have been sub- 

 ject to much interpretation, and have 

 yielded under the nursing hand of 'pro- 

 ductive' scholai'ship, meanings which in 

 reality they do not contain. It seems there- 

 fore worth while to reconsider what is the 

 great generalization at which he arrived; 

 and to those interested in the historical side 

 of embryology, this attempt to follow the 

 reasoning of a masterly investigator may 

 be not unwelcome. 



I. 



THE PREVAILING VIEW THAT THE EMBRYO 



PASSES THROUGH THE ADULT STAGES 



OP LOWER ANIMALS. 



At the time Avhen the first volume of the 

 'Observations and Reflection.s on the De- 

 velopment of Animals' was published 

 (1828), no propositions in embryology en- 



