PRINCIPAL SYSTEMS OF ZOOLOGY 201 



present preclude the possibility of an association of the Rhizopods 

 with the Algas. This would almost seem natural, when we consider 

 that the vesicles of many Fuci contain a viscid, filamentous substance, 

 so similar to that protruded from the body of the Rhizopods, that 

 the most careful microscopic examination does not disclose the 

 slightest difference in its structure from that Avhich mainly forms 

 the body of Rhizopods. The discovery by Schultze^ of what he con- 

 siders as the germinal granules of these beings by no means settles 

 this question, though we have similar ovoid masses in Algas, and 

 though, among the latter, locomotive forms are also very numerous. 

 With reference to the Infusoria, I have long since expressed my 

 conviction that they are an unnatural combination of the most 

 heterogeneous beings. A large number of them, the Desmidieae and 

 Volvocinas, are locomotive Algas. Indeed, recent investigations seem 

 to have established beyond all question, the fact that all the In- 

 fusoria Anentera of Ehrenberg are Algae. The Enterodela, however, 

 are true animals, but belong to two very distinct types, for the Vorti- 

 cellidze differ entirely from all others. Indeed, they are in my opinion 

 the only independent animals of that group, and so far from having 

 any natural affinity with the other Enterodela, I do not doubt that 

 their true place is by the side of Bryozoa, among Mollusks, as I shall 

 attempt to show presently. Isolated observations which I have been 

 able to make upon Paramecium, Opalina, and the like, seem to me 

 sufficient to justify the assumption that they disclose the true nature 

 of the bulk of this group. I have seen, for instance, a Planaria lay 

 esfgs out of which Paramecium were born, which undenvent all the 

 changes these animals are known to undergo up to the time of their 

 contraction into a chrysalis state; while the Opalina is hatched from 

 Distoma eggs. I shall publish the details of these observations on 

 another occasion. But if it can be shown that two such types as 

 Paramecium and Opalina are the progeny of Worms, it seems to 

 me to follow that all the Enterodela, with the exception of the Vorti- 

 cellidae, must be considered as the embryonic condition of that host 

 of Worms, both parasitic and free, the metamorphosis of which is 

 still unstudied. In this connection I might further remark that the 

 time is not long past when Cercaria was also considered as belong- 

 ing to the class of Infusoria, though at present no one doubts that 



^Maximilian S. Schultze, Ueber den Organismus der Polythalamien (Leipzig, 1854). 



