PREVIOUS INTERPRETATIONS OF CNIDARIA 93 



been earlier defended by Hjalmar Broch, the author of articles 

 on Hydroidea and Narcomedusae in the extensive German 

 work Handhich der Zoologie (1924), edited by Kiikenthal- 

 Krumbach. Broch considered budding to be a common and 

 a very old property which had thus been introduced indepen- 

 dently in the planktonic Narcomedusae. This violates the 

 generally accepted rule that budding is due to the sessile 

 way of life and that it can be transferred afterwards to descen- 

 dants which have later adopted the pelagic way of life (e.g. 

 parasitic larvae of some Narcomedusae). Another difficulty 

 the adherents to the actinula hypothesis meet is the question 

 of the origin of Hydromedusae in the benthonic cormi 

 (colonies). One can refer here to the proposition made by 

 Goette (1912) who tried to derive the metagenetic forms of 

 Hydromedusae from the sessile medusoids. 



Here we must briefly touch one of the extreme and least 

 probable hypotheses which try to derive the Cnidaria from 

 the primitive forms that live in the pelagic zone. This 

 is the so-called medusom theory which has been proposed 

 by F. Moser (1921-1924). During her study of Siphonophora 

 she came to the idea that the larvae of Siphonophora might 

 correspond exactly to the primitive form of Hydrozoa and, 

 in connection with this— even if she does not state it expli- 

 citly — of all Cnidaria. First numxcrous medusoid organs have 

 developed which have later evolved into full members i.e. 

 persons (suhindivides) of colonies. In the benthonic colonies of 

 the Hydroidea which are a result of a later development, 

 hydromedusae and polyps have again evolved on their own 

 account. Hyman (1940 I: 636), too, considers this hypothesis 

 to be "not very convincing," and I have submitted it to a 

 severe criticism (Hadzi, 1926) in w^hich I have shown its 

 complete untenability. It is certainly absurd to try to find 

 the origin of Hydrozoa in Siphonophora, even in their most 

 primitive forms, since there can be no doubt that they reaUy 

 represent the climax of a progressive and specializing evolution 

 of the colony of Hydrozoa. The very first premise in the 



