216 PROCEEDINGS OF THE AMERICAN ACADEMY. 



in his lectures I cannot remember that they were ever treated directly 

 by anything more than incidental references, although embryology was 

 very often the principal theme. 



Nevertheless, I must have got directly from him, subsequently to 1858, 

 the principles of this branch of research, and through this and the abun- 

 dant materials furnished by the collections he had purchased and placed 

 so freely at my disposal, I soon began to find that the correlations of the 

 epembryonic stages and their use in studying the natural affinities of 

 animals were practically an infinite field for work and discovery. 



Although within a year after the beginning of my life as a student 

 under Louis Agassiz I liad become an evolutionist, this theoretical change 

 of position altered in no essential way the conceptions I had at first 

 received from him, nor the use we both made of them in classifying and 

 arranging forms. This experience demonstrated to my mind the absurd- 

 ity of disputing the claims of any author to the discovery of a series of 

 facts and their correlations because of his misinterpretation of their more 

 remote relations or general meaning. It is of some importance to notice 

 this, because it is the rule now to attribute Von Baer's and his predecessors' 

 and Louis Agassiz's discoveries in this line to Haeckek This eminent 

 author has, indeed, given one of the most modern definitions of this law, 

 and has named it the ' law of biogenesis.' Ilaeckel's discoveries in em- 

 bryology are sufficiently great without swelling the list with false entries, 

 but it will probably be a long time before naturalists realize and acknowl- 

 edge this error. Some of the most eminent embryologists in this country 

 have ado[)ted the Haeckelian nomenclature without sufficient critical 

 examination of the term under discussion. The so called Haeckelian 

 'law of biogenesis' is really Agassiz's law of embryological recapitula- 

 tion restated in the terms of evolution. 



It has surprised me that serious objections to the use of the word 

 ' biogenesis ' in this connection have not been made. This word has 

 been long employed in another sense, as antithetical to ' abiogenesis.' 

 The latter has been for many years applied to the theory of the genera- 

 tion of living from inorganic matter, and tlie former to the theory assert- 

 ing that living matter can originate only from living matter ; the use of 

 the phrase ' the law of biogenesis ' is consequently inappropriate, since 

 neither did Agassiz's nor Haeckel's discoveries cover so much ground. 

 The former gave us a law for the correlations of the earlier stages of 

 ontogeny with phylogeny. Tliis cannot be called ' the law of biogene- 

 sis,' since that has been long ago stated as the law of the origin and 

 continuity of organism, or, in other words, the genesis and continuity of 



