THE GONOPHORES OF THE HYDEOCORALLIN^. 199 



in the degeneration of medusae, may lead to the conclusion that 

 these gonophores of the Hydrocorallifies are also degenerate 

 medusae; and it is necessary to issue a warning that this is 

 probably not the case. 



That the medusa of Millepora is not degenerate but primi- 

 tive in its simplicity must be apparent. 



In the course of its development there is no abbreviation nor 

 any trace of organs that were at one time functional and have 

 since become rudimentary. Moreover, it cannot be considered 

 at all probable that a free-swimming medusa, bearing immature 

 spermatozoa, would have lost its mouth, tentacles, sensory organs, 

 endoderm canals, and velum ; or, if it is a degenerate medusa, 

 that the development of these organs would be postponed until 

 after its escape. 



The only view that seems to me to be at all tenable is the 

 one that considers the medusa of Millepora to be primitive in 

 its simplicity. 



As regards the male gonophores of Allopora and Disticho- 

 pora, there is without doubt a close similarity in appearance 

 between certain stages in the development of the male gono- 

 phores of both these genera and the younger stages of the 

 medusae of such forms as Pennaria and other Tubularians (cf. 

 this paper, PI. XIV, and Weismann (12), pi. xvii. fig. 3) ; and 

 the manubrium of Allopora is undoubtedly closely similar in 

 general appearance to the manubrium of the adelocodonic 

 gonophore of many of -the Tubularise. In fact, the gono- 

 phores of some of the Hydroidea, such as Clava (Allman) and 

 Corydendrium (Weismann), are much less like adelocodonic 

 medusae, even when they reach their full development, than 

 are these gonophores of Allopora and Distichopora. 



If it could be shown that the inner membrane covering the 

 spermarium is derived from the ectoderm and is not endodermic 

 as I have described it, and that structures corresponding to the 

 "glockenkern" do occur in the development of these gonophores, 

 then my principal objections to the view that they are degene- 

 rate medusae would fall to the ground. A very careful examina- 

 tion of my sections of gonophores in all stages of development 



7—2 



