LIFE-HISTORY OF CRASPEDACUSTA RYDERI. 44! 



Since we now know the life-history, we are better able to 

 discuss the systematic position of Craspedacusta. First, we find 

 a complete alternation of generations. By this I mean that we 

 have hydroids which give rise to medusae by means of buds, 

 an asexual process, and medusa?, which, by a sexual process, 

 give rise to the hydroids. If Mayer is correct, it is evident that 

 the medusa of Craspedacusta is Leptomedusan in structure and 

 in development, with the exception of the origin of the otoliths. 

 Most certainly it is not a transformed actinula. It arises as a 

 bud from the hydroid. The bell is formed as in the Lepto- 

 medusae and the tentacles are outgrowths from the margin of the 

 bell. The medusa is a typical completely formed medusa when 

 it breaks away from the hydroid. For the details of this process, 

 see my former paper (Payne, '24). I do not see how the hydroid 

 of Craspedacusta can be interpreted in any other way than as a 

 hydroid. There are no tentacles, but in other respects it is a 

 typical hydroid and behaves as such. Is it a Tubularian or a 

 Campanularian hydroid? The only essential difference between 

 the two groups is the presence of hydro- and gonothecae in 

 Campanularia and their absence in Tubularia. The basal half 

 or two thirds of the hydroid of Craspedacusta is surrounded by a 

 covering which is in part a secretion, but whether it could be 

 called a hydrotheca and the hydroid classed with the Campanu- 

 laria is doubtful. If the covering is not a hydrotheca, perhaps 

 the hydroid could be classed as a Tubularian. According to 

 the present classifications there is no such thing as a Trachy- 

 medusan hydroid. 



The medusa of Craspedacusta, with the exception of the 

 endodermal origin of the otoliths, is Leptomedusan . This charac- 

 teristic is Trachymedusan, but in so far as I can judge, it is the 

 only exclusive Trachymedusan characteristic which the medusa 

 has. Where then, should Craspedacusta be placed? I do not 

 see how we can place it in any of the existing groups as these 

 groups are now defined. It would seem to me that it is more 

 closely related to the Leptomedusee, however. While I do not 

 care to place Craspedacusta in either of these groups as they are 

 now, neither do I care to create a new position for it. This 

 must wait for more extensive studies upon the life histories of 





