18 



be considered as belonging to the type (trunk) of the Polyzoa, since the accomplished de- 

 velopment of its completely organised digestive system, which is so entirely foreign to the 

 Hydrozoa, sufficiently stamps it as a Polyzoon. 



„Finally we remark that it may appear strange that the Rhabdopleura, which in all 

 probability is of so ancient origin, should possess a similar, although modified, form of ten- 

 tacular Corona (bilateral) to that which belongs to most fresh water Polyzoa (P. hippocrepia, 

 Gervais, Phylactolsemata Allman) and which is usually considered as a more perfect formation 

 than the circular (in P. infundibulata G). It is however possible, that the first is properly 

 the original form, from which the latter has subsequently arisen. The fresh waters appear, 

 asHseckel lately has remarked, to contain the direct descendents of some of the eldest animal 

 forms which, by reason of the less complicated accidents of the fresh waters, have often in 

 the „struggle for life", only slightly altered their original more simple structure; as for 

 instance: among the coelenterates, the Hydra; among the Rhizopods, the Actinophrys, Gromia 

 and the shell-less Eadiolari lately discovered by Focke; among the fish, the Ganoida &c. 



