M. E. Claparede ow Actinophrys Sol. 211 



branipo7^a, or Flustra, which is impressed on the outer surface of 

 the Oyster; and thence a further proof is afforded that the 

 Pholas was external, and served as a mould to the Oyster-shell, 

 and is not enclosed within its substance. 



" Yours truly, 



"J.E. Gray/' 



Greenwich, Feb. 17, 1855. 



XX. — On Actinophrys Sol. By E. Claparede*. 



[With a Plate.] 



It can scarcely be doubted that nearly all true Infusoi-ia, that 

 is to say, all animal Infusoria, possess at least an indication of 

 a circulation, by which expression we would refer to the so-called 

 contractile vesicles , without however at present deciding as to the 

 kind of circulation, or whether it be a circulation of blood or 

 water. Nevertheless this structure has hitherto remained un- 

 discovered in many Infusoria, apparently of animal nature ; in 

 one very pretty animalcule, the Actinophnjs Sol, especially, it 

 has been overlooked by nearly all observers. As, however, I 

 recently met unexpectedly with a considerable number of this 

 Actinophrys in a bottle where I had not previously observed 

 them, I was struck by a peculiar organ possessed by all the in- 

 dividuals, which puzzled me at first, but soon showed itself to 

 be undoubtedly a contractile vesicle placed in a very remarkable 

 position. ■' "'"" '>'^ 



Ehrenberg, in describing Actinophnjs Sol in his great work on 

 the Infusoria, of course endeavoured to discover in it the stomach 

 cells, mouth and anus required by his theory. Accordingly, as 

 might be expected, Actinophrys was said to capture animalcules 

 and microscopic plants by means of a proboscis, digest them in 

 connected stomachal cells, and get rid of the indigestible portions 

 through an anal opening. Later observers (Dujardin, Kolliker, 

 &c.) could find nothing of this, and affirmed either that the 

 animal did not eat, or that it converted any part of its body at 

 pleasure into a mouth or an anus. Kolliker, in particular, con- 

 jectured that Ehrenberg had seen a process, which would gra- 

 dually have formed a tentacle, and had taken it for a protrusible 

 proboscis. Nevertheless Ehrenberg's assertions as regards the 

 n.outh are by no means groundless; his observations are per- 

 fectly correct, but his explanation of them quite inadmissible, as 

 will be seen from what follows. 



When seen from above (PI. VIII. fig. 1), Actinophrys Sol ap- 



* Abridged from Miiller's Archiv for December 1854. 



14* 



