174 KEPRESENTATION OF THE 



may be arrived at by a comparison of the different modifi- 

 cations of reproductive apparatus occurring among the 

 Polypifera themselves, as in this single group we find a 

 transition, and that even among closely allied species, from 

 cases in which the structures ministering to reproduction 

 are integral parts of the system, and organs of very simple 

 form, to others in which they appear as detached zooids, 

 having the characters of distinct and well organized ani- 

 mals. A gradation is here presented to us of the most 

 continuous kind, from the spermatic and ovarian follicles of 

 the Hydra fusca to the Medusae just mentioned, whose iso- 

 lation from the parent stock, free powers of locomotion, 

 colossal size, and development of organization, appear almost 

 to raise them to a higher type of animal life. As Professor 

 Huxley remarks, " in passing from Hydra to Rhizostoma, 

 we thus see the reproductive organs acquiring a greater and 

 greater relative mass, when compared with the organism 

 from which they spring, and, as it were, grouping round 

 themselves and subordinating to their own perfection a 

 greater and greater number of morphological elements. 

 First, they are parts of the body wall, indistinguishable in 

 form from the rest ; then they are distinct sacs ; then they 

 are sacs with a gonocalyx [bell-shaped envelope] ; then 

 that gonocalyx becomes a well developed contractile organ ; 

 next the reproductive apparatus is detached, and swims 

 about independently by means of its gonocalyx or umbrella ; 

 and, finally, it acquires total independence, feeding and 

 nourishing itself, and attaining the most complex organiza- 

 tion exhibited by the class to which its originator belongs."* 

 8. Granting, however, on the grounds now alleged, 

 that a general community of nature may be admitted be- 

 tween the reproductive organs of the higher animals, and 

 the gamomorphic zooids of the lower species in which alter- 



* Oceanic Hydrozoa, p. 18. 



