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On the Development of Actinophrys sol. 



By Mr. James Fullagar, Honorary Assistant Secretary of the 

 East Kent Natural History Society. 



Read Sept. 21th, 1875. 



Having for some time past been occupied in examining' 

 Actinophrys sol (a number of specimens of which I found in a 

 glass cell wherein I had been watching some rotifers), my attention 

 was called to the manner of their taking food, and also of their re- 

 production by fission. This formed the subject of a paper, pub- 

 lished, with sketches, in the May number of " Science Gossip." 

 The present communication consists of what I afterwards observed 

 with reference to some remarkable changes through which the 

 A. sol passes. I had on several occasions witnessed what is 

 termed " conjugation " — that is, when two or more Actinophrys 

 approach each other, and at first an entanglement of their spines 

 takes place ; then, coming closer to each other, they gradually 

 become fused into one mass. According to Prichard, in his work 

 on the Infusoria, this was by the early observers considered a 

 reproductive act — a sort of copulation between two individuals ; but, 

 he says, " the tendency of opinion at the present day is to deny it 

 this nature, and to treat it as little more than an accidental 

 phenomenon without apparent object or aim. Nevertheless, its 

 occurrence is so frequent, and its process of so complete a charac- 

 ter, that it is hard to believe it to be in vain, and of no purpose in 

 the economy of the Actinophrys." The Actinophrys thus fused to- 

 gether may be of any number, from two to twelve, whicli number 

 may be told by the outward position of the spines, as they do not 

 entirely lose their outward or individual form, but the parts where 

 they unite become intermingled, and are so fused with one another 

 that they appear as one body. 



The following observations were principally taken from a group 



