162 THE EVOLUTION OF THE METAZOA 



We cannot accept Garstang's thesis (W. Garstang, 1946) 

 that the Siphonophora are "bud communities." This thesis is 

 quite untenable because buds are in fact the asexual primordia 

 of these subindividuals. Thus the *'bud communities" are in 

 fact true cormi (usually called colonies) which is also true 

 for the chondrophore Siphonophora; Garstang, however, 

 considers them as polypoid individuals. 



With regard to the origin of the Siphonophora I again 

 maintain that it is wrong to point in this connection to the 

 plank tonic larvae (planula and actinula) and to try to deduce 

 the Siphonophora from them as has recently been done by 

 E. Leloup (1929) and Hyman (1940). We can easily under- 

 stand that as a consequence of a long progressive evolution 

 within the frame of the subtype of the Siphonophora the 

 ontogenetic process had also been modified and that the 

 siphonula had evolved as a special larval form from the 

 planula (and the ratarula as an even more specialized form 

 which had been developed by the Chondrophora) so that 

 it had developed into an Anlage of the cormus (Fig. 46 a). 

 It can easily be understood why a primary polyp (i.e. a 

 primary gastrozooid) develops as a kind of an Anlage of 

 an oozooid on the larva of the Siphonophora and why 

 it later grows as a monopodium into the Anlage of the 

 cormus, i.e. into the basis of the cormus, into the impersonal 

 stock on which the first members of the family bud as subindi- 

 viduals either as the first swimming bell w^hich is true for the 

 subgroup Cylycophorae, or as an Anlage of the pneumato- 

 phores which is true for the Pneumatophorae. 



The Siphonophora must be considered as the climax in the 

 evolution not only of the Hydrozoa but also of the Cnidaria 

 as a whole. 



Because of our imperfect knowledge of the whole develop- 

 ment cycle of a large number of the Hydroidea we must 

 for the time being still accept the existence of a double 

 system, i.e. that of the hydropolyps and that of the hydro- 

 medusae. This certainly is an anomaly which will soon have 



