12-i EMBRYOLOGY 



of adhesion (septal nodes, Haeckel), Avhich are present in 

 the Ephjropsida3 on the external side of the row of gastral 

 filaments, as the remains of the coluraellfe corresponding to 

 these funnels. The Semteostomfe and the Rhizostoma? are 

 derived by further metamorphosis from the Ephyra form. 



If we imagine that in the above-supposed attached an- 

 cestral form a division of labour made its appearance of 

 such a natui'e that the power of non-sexual reproduction 

 was retained by the attached scyphopolyp form, while the 

 generation of the sexual products was confined to the free- 

 swimming (medusa) forms, resulting from the transverse 

 division, the origin of the kind of alternation of generations 

 characteristic of the Scypliomedusfe would in this way be 

 explained. 



Whereas the tendency formerly was to unite the Hydrozoa 

 and iScyphomedusee into a common group, in moi-e recent 

 times our conception has led to a complete separation of 

 these two divisions. O. und R. Hertwig's (No. 9) doctrine 

 of the diphyletic origin of the medusa form and their dis- 

 tinguishing between Ectocarps and Entocarps first prepared 

 the way for this separation. Although various persons, 

 especially Claits (No. 102), had previously placed importance 

 upon the presence or absence of the t^nioloe, which are 

 also possessed by the polyps, as characteristic differences, 

 nevertheless the sharp separation between the scyphopolyps 

 and the hydropolyps was first established by Goette (No. 

 105). On the other hand, the observations of Goette, 

 especially the discovery of the ectodermal nature of the 

 oesophagus in the Scyphistoma?, have led to approximating 

 this group to the Anthozoa, so that recently various authors 

 (Lang, Hatschek), in accord with Goette, have united the 

 two groups as Scyphozoa. It must be mentioned, however, 

 that the scyphopolyps are separated from the Anthozoa by 

 the possession of septal infundibula, and by the ectodermal 

 origin of the longitudinal muscles, to which are to be 

 added as distinctive characters differences in the origin of 

 the first four gastral pouches and many differences in 

 general histological character — greater development of the 

 mesodermal tissue in the Anthozoa. Even though we 



