64 ANIMAL PARASITES AND MESSMATES. 



that to wliich I had come twenty years before, and that 

 it is not a very hapjoy innovation to change the term 

 polyps for zoophytes. It is the more surprising that this 

 naturahst has forgotten to quote my oi)inion, since at the 

 congress of naturaHsts at Hanover, in 1866, I had placed 

 this question on the agenda for an ordinary meeting. 



I maintained, in opposition to the opinion of the 

 naturalists whose authority had been especially recog- 

 nized in the matter (Osc. Schmidt, who was present, 

 among others), that sponges are lower polyps, whether 

 they are regarded as to their development or their 

 organization. 



This group, so remarkable in form, so varied in 

 colour and appearance, very often affords examples of 

 animals which live wdth them as true messmates ; and 

 we find the same relations established between them in 

 both hemispheres. As we observe rhizophales on crabs 

 and soldier-crabs, and pinnotheres on bivalve molluscs, 

 so we find that the sjDonges of the Indian Seas or of 

 Japan harbour the same messmates which we discover 

 on them in the Northern Seas or the Atlantic. 



In the sea of Japan is found a very remarkable 

 sponge, generally known by the name of Hyalonema, 

 It is a bundle of spicules like threads of glass, which 

 seem artificially tied together, and on the surface of 

 which we regularly find a polyp of the genus Polythoa. 

 The nature of this sponge, and its relations with the 

 polyps which surround it, have been discussed for many 

 years. Ehrenberg had recognized the polyp Polythoa 

 around the spicules, but the Hyalonema was considered 

 by him as an artificial product. The PolytlwiB were 

 regarded as only a case in which had been placed this 



