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NOTE ON THE TERMINOLOGY OF THE ORGANS OF THE HYDROZOA. 



Since I have strongly acknowledged the value of Professor AUman's contributions to our 

 knowledge of the Hydrozoa, and since I have gladly made use of certain of the terms which 

 he has invented (e. g. gonopUore), I feel bound to assign my reasons for not adopting the whole 

 of his terminology. 



The transition between what Professor Allman terms sporosacs and his '■'Medusa' is 

 so gradual, that I know not where the line of demarcation is to be drawn between the two. 

 If the title of sporosac, however, could be applied to such reproductive organs as those of 

 Hjjdracthiia, which are simple sacs without a trace of medusoid structure, I think the 

 term would be useful. 



"Ectotheca" and "blastostyle" appear to me to be very good terms when applied to 

 the central axis and the capsule of such " compound gonophores " as those of Laomedea; 

 but I think that when the stalk of the gonophores of Tabularia (with which the stem 

 of similar organs in the Phijsophondm is homologous) is also called blastostyle, the same 

 name is apphed to different things. The stem of the " gonoblastidium " of the Physophorid 

 contains, I apprehend, the representatives of both the blastostyle and the ectotheca of Laomedea. 



Again, the " generative polypes " of Hydradinia are surely homologous with the stalks 

 of the gonophores in Tiihdaria; but to these, and, as I think, with justice, Professor Allman 

 .does not apply the term "blastostyle." 



When we know a medusiform body to be simply the detached reproductive organ 

 of a hydrozoon, it seems to be better to avoid all chance of confounding it with a truly 

 independent organism. I have, therefore, abstained from using the word " Medusa," except 

 in the sense defined at p. 21 ; and for me Professor AUman's Medusm are medusiform 

 gonophores. 



Finally, the term manubrium should, I think, be restricted to the central polype-like sac 

 of a medusiform gonophore, which is surely the homologue of the whole sporosac of 

 Hydradinia, and not of its central cavity only. 



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