HTDROZOA. 75 



guished from ' gamogenesis,' in -which the ovum, 

 to be developed, must first be brought into con- 

 tact with spermatozoa. 



But such modifications are, in nature, less 

 distinct from one another than the systematic 

 definitions just given might appear to imply. 

 Furthermore, recent investigations on the de- 

 velopment of Insects and Crustaceans have tended 

 alike to confuse our old-established notions of 

 animal individuality and of the true nature of 

 the generative process. For certain Insect ova 

 have been observed to undergo development in 

 the ordinary manner, though no previous contact 

 with spermatozoa had taken place. And in un- 

 impregnated female Vertehrata ovarian tumours 

 are said sometimes to occur, which contain traces 

 of hair, teeth, bone, nerves, and other tissues pro- 

 per to the adult organism. If, therefore, cases 

 exist in which the influence of a male element 

 seems rather accessor)^ than essential to the normal 

 evolution of the germ ; nay, can even be dispensed 

 with, there are others in which, without such 

 influence, no proper individuality is manifested, 

 though development, to a certain extent, must as- 

 suredly be considered to have taken place. For 

 the present we have preferred to advocate the 

 views entertained on these disputed points by 

 Professors Huxley and Carpenter, while, to avoid 

 needless ambiguity, we have thought it better to 

 employ the precise terminology which the former 

 naturalist has suggested. 



But other attempts have been made to explain 

 the phenomena in question. Steenstrup, followed 

 in Britain by the late Professor E. Forbes, and a 

 host of minor investigators, proposed to consider 



