HISTORY OF THE FERTILIZATION PROBLEM n 



tension or inclination to assume the same form of trans- 

 formation and movement. Fertilization is thus not 

 a process of union and fusion as in ordinary chemical 

 combination, but a catalytic process, as denned above. 



This point of view deserves to be emphasized as one 

 of the first attempts at a physicochemical explanation 

 of fertilization. 



For some time naturalists were divided between the 

 two points of view, viz., that of Prevost and Dumas, 

 that the sperm penetrated into the egg, and that of 

 Kolliker and Bischoff, that it acted by contact. Lalle- 

 mand (1841) well expresses the view of those who be- 

 lieved in the union of the ovum and spermatozoon. 



Each of the sexes furnishes material already organized and 



living A fluid obviously can not transmit form and life 



which it does not possess Fertilization is the union of two 



living parts which mutually complete each other and develop in 



common When one embraces in a single point of view the 



reproduction of all living beings, one arrives at the following more 

 general formula: Reproduction is the separation of a living part 

 which may either develop separately or acquire from another living 

 part the supplementary elements necessary for the ulterior develop- 

 ment of a being similar to the type The preservation of 



the type is due to the extension of the same act which has produced 

 the development of each individual being. 



This is the most complete statement of the principle 

 of genetic continuity that I have found in the literature 

 of this period. 



These observations and conclusions were found on 

 the eve and early morrow of the great biological general- 

 ization, the cell theory. Though Schwann interpreted 

 the ovum as a cell (1838), this view did not at once 

 become dominant and was generally accepted only after 



