36 Prof. Mtiller on the Development 



produced from Strobila, as described by Sars. For the young 

 of Medusa aurita, Cyanaa capillata, and Cephea Wagneri, is in 

 part polype-like, and the young of the two former multiplies by 

 the production of larvae, i. e. by means of budding and fission, 

 before it attains the perfect sexual form. Some have believed, 

 that, as a consequence, the class of Polypes and Medusae must be 

 united ; and I was myself of the same opinion. Now, however, 

 from my observations upon Synapta, and their necessary conse- 

 quences, it would seem that these deductions have been pushed 

 too far, and that we must draw a preliminary distinction between 

 the alternation of generations and heterogony. The facts dis- 

 covered by Sars belong to the proper alternation of generations. 

 When the young Medusa aurita has a polype-like form, and fixes 

 itself, it is by no means a Polype ; it rather deserves the name 

 of a Polype-like Medusa-larva. 



As to the facts discovered by R. Wagner, Loven, Krohn, and 

 Van Beneden, it is for the present uncertain whether they are 

 cases of alternation or of heterogony. 



For although the Polypes of the genera Coryne, Syncoryne, 

 Campanularia, Tubularia,Eudendrium, produce by gemmation true 

 Medusae with gastric vessels, and even in part with the otolithe 

 of Medusa;, yet no one has ever seen what sort of young these 

 Medusae produce, nor whether their sexual brood consists of 

 Polypes of these genera. 



On the other hand, the sexual propagation of these Polypes is 

 already known. Loven has seen the ova of Campanularia geni- 

 culata, and the ciliated Polype-embryo which proceeds from them, 

 and (which is still more important) has traced the development 

 of the Polype from the latter. 



The seminal organs of Tubularia and of Eudendrium have been 

 discovered by Krohn and Kolliker, those of Coryne squamata by 

 Rathke, those of Campanularia geniculata by Max. Schulze. 



It follows, then, that these genera of Polypes produce two 

 quite distinct generations, of which one is homogonous, the 

 other heterogenous. The heterogonous products of those spe- 

 cies of Polypes form a connected series of Medusae, so that the 

 homogonous and heterogonous generations of the Polypes form 

 parallel series. Do different kinds of Synaptce also possess hete- 

 rogonous generations, do they produce mollusks, and do these 

 also form parallel series ? 



The attention of naturalists must now be especially directed 

 to the nature of the brood produced by those Medusae which 

 proceed from Polypes. The young, formed by gemmation, of a 

 few allied Medusae (Sars, Forbes), which I have myself observed, 

 are again Medusae ; but do the former also produce similar Me- 

 dusae by their sexual generation ? 



