ALTERNATION OF GENERATIONS. 121 



to consider the polype form as a rudimentary phase, com- 

 parable to that occurring among the Trematoda, and to re- 

 gard as typical the Medusa form, which is an animal of 

 much more conspicuous appearance, of apparently higher 

 organization/ endued with the power of locomotion, and 

 having true sexual organs in distinct individuals. Such, 

 indeed, is the view taken by Steenstrup and several other 

 authors, even by those who occasionally speak of the medu- 

 soid progeny of the Hydraform polypes as mere detached 

 generative organs. Thus Prof. Owen observes " The 

 nutritive gemmiparous polypiform individuals in all the 

 compound Radiaries would seem, rather than the oviparous 

 medusiform ones, to manifest the typical form of the 

 species. . . . Superadd, however, distinct nutritive 

 and circulating organs to the free-moving ovigerous indi- 

 vidual from the rooted polype, and prolong its existence, 

 and it would then cease to have the ancillary character of a 

 nurse to the ova of the fixed individuals, and would assume 

 that of the perfected form of the species ; and such in fact 

 is the case with the larger gelatinous Radiaries called 

 Medusa." * 



Now, in so far as perfection means the possession of a 

 more conspicuous organization, it is not of course to be 

 denied that the Medusa is in advance of the polype ; but 

 as regards the selection of the phase to be taken as the 

 typical form of the species, I do not see how we can avoid 

 these conclusions 



1. That the Medusoids derived from the compound 

 polypes (Sertularida and others) formerly ranked as a dis- 

 tinct order under the name of Gymnophthalmatous (or bare- 

 eyed) Medusa3 are really homologues of the parts of re- 

 production, inasmuch as they pass by a continuous grada- 

 tion into generative organs of the simplest kind. 



* Parthenogenesis, p. 12. 



