78 HTDROZOA. 



bear the same morphological relation to their 

 reproductive bodies. Extend the case to these; 

 let Velella, for example, be henceforth the larva 

 of its free medusiform gonophores, and the doc- 

 trine which we have contested is at once seen to 

 become untenable. 



Another explanation emanated from Professor 

 Owen. His ingenious theory of ** parthenogenesis " 

 supposed that the primitive result of each genera- 

 tive act retains within its body unchanged a cer- 

 tain portion of the germ-mass from which it was 

 first evolved, together "with so much of the 

 spermatic force inherited by the retained germ- 

 cells from the parent-cell or germ-vesicle as 

 suffices to set on foot and maintain the same 

 series of formative actions as those which consti- 

 tuted the individual containing them." So that 

 " every successive generation, or series of sponta- 

 neous fissions, of the primary impregnated germ- 

 cell, must weaken the spermatic force transmitted 

 to such successive generations of cells." Or, to 

 confine ourselves to the class under consideration, 

 that a Corynid produced, as the resultants of the 

 germ-cells and spermatic force stored up within it, 

 successions of free or fixed gonophores, until the 

 generative force became exhausted. But here, at 

 least, it can be proved, that the unchanged germ- 

 masses alluded to have no objective existence, 

 while the more subjective spermatic force, in 

 these, as in all other, animals, has hitherto suc- 

 ceeded in escaping the ken of the anatomist. 



