VII PAETHENOGENESIS 245 



statement of the signification which such inquiries as 

 his have in the present state of knowledge. Harvey's 

 dictum, " Omne vivum ex ovo/' expressed a great law, 

 which had to be qualified when the researches of 

 Trembley and others made known, among Polyps, and 

 Worms, and Protozoa, reproduction by fission. To 

 this rapidly succeeded the recognition of a modified 

 fission, in which the animal did not divide into equal 

 parts, nor exhibit the power of reproduction of the 

 whole animal in artificially detached portions of its 

 body ; but in which special sprouts or buds were found 

 to be prepared and detached spontaneously, becoming 

 then developed into perfect animals. This process 

 received the name of gemmation, and was stated to 

 occur in polyps and also in the plant-lice. Parallels 

 for these methods of reproduction in animals were 

 readily recognised in plants, in the multiplication 

 by seed, by cuttings or shoots, and by separable 

 buds. A broad line was drawn between "buds" and 

 " eggs," however egg-like the former might appear, in 

 the assumption that eggs were special bodies of a 

 peculiar structure, destined to be "fertilised" by the 

 spermatozoa of the male after which process only 

 could they develop. These distinctions, some twenty 

 years ago, were the more firmly impressed in the minds 

 of biologists by the then recently acquired knowledge 

 of the process of fertilisation or impregnation. Then 

 came the demonstration by Siebold of the capacity for 

 development of true eggs, even when not impregnated. 

 The sharpness of the limit between buds and eggs was 

 by this at once destroyed ; and the closely following 



