212 THE AUSTRALIAN HYDROMEDUS^E, 



In this manner he brings all but five of those genera which 

 were investigated by him into the group with Medusoid Gono- 

 phores, my Hydrornedusinae. But even these five, with the 

 exception of Hydi-a (I.e. pag. 245 fl\), he finally considers to be 

 Hydromedusae with medusoid buds. These conclusions are 

 mainly based on the observations made by Weismann on the 

 wandering of the generative cells, one of the most important 

 discoveries concerning our animals, which were ever made, 

 statements which also I had occasion to confirm in my paper on 

 Eucopella. 



The medusae certainly are more recent than the Hyclroid colonies, 

 and there can be no doubt, that the Hydroid colonies must have 

 been propagated sexually before Medusas were formed. It would 

 appear very strange if no such ancestral forms should have come 

 down to us as it is clear that now the free Medusae are in many 

 cases worse than useless and have therefore again become rudi- 

 mentary. The cases of Gonophores which show traces of a 

 Medusoid structure doubtlessly belong partly to the Hydro- 

 rnedusinae as they have really descended from Hydromedusae with 

 free Zooids. On the other hand it is certainly possible that some 

 of these are not rudimentary Medusae but real Polypostyles. It 

 is only a case of greater or smaller probability, and probability 

 always is a subjective feeling. Weismann thinks it probable that 

 these Gonophores are rudimentary Medusae, and his opinion is of 

 great weight if we consider the excellency of his work on the 

 subject, and I dare say he is quite right. 



I for my own part have not been convinced by his publication, 

 and consider it as probable that Gonophores, which are not 

 rudimentary Medusae, do exist. Whether all the forms, which 

 according to my idea, have other Gonophores, and therefore ai'e 

 placed among the Hydropolypinae really belong there, is another 

 question. In doubtful cases I decided according to the position of 

 the Gonophore for the reasons given in my former paper 

 (Zoologischer Anzeiger) on this subject. 



The Hydroid colonies are often overgrown by tufts of Diatoms 

 and other Protista, and a Medusa produced near the base of the 



