Dr. L. Plate on the Genus Acinetoides. 207 



nearly allied Acinetae frequently have swarm-buds with a 

 ciliation arranged in the same or a similar manner, of which 

 the Suctorian described in the next article, whose nearest 

 ally is undoubtedly Dendrocometes ijaradoxus^ furnishes a 

 good example. We may therefore justly conclude from the 

 ciliary clothing of the Acinetan buds that the Suctoria are 

 genealogically connected with the Ciliata, a conclusion which 

 is the more naturally arrived at because we know many 

 Ciliated Infusoria which have lost their buccal aperture by 

 adaptation to peculiar conditions of life. 



In 8])haroijlirya magna Maupas * has detected tentacles 

 which greatly resemble the pseudopodia of the Rhizopoda. 

 They are contractile rods composed of a plasmatic axis and a 

 cortical layer, and therefore are not hollow, and are not con- 

 tinued into the proper body of the Acinetan. They terminate 

 in a knob which very quickly kills and then holds fast such 

 Infusoria as may come in contact with it. Then the tentacle 

 increases greatly in thickness, which Maupas, probably witii 

 justice, places to the account of an invisible current of plasma 

 flowing out from the Suctorian to the prey and probably 

 penetrating into it. Finally a current in the opposite direc- 

 tion is observed, which conveys the plasma of the captured 

 animal to the body of the ISphcerophrya. The inception of 

 nourishment thereiore takes place here in exactly the same 

 manner as with true pseudopodia, namely without any 

 pumping movement. Such organs, however, are by no 

 means characteristic of the whole class of the Acinetffi, but 

 are at present known only in that single form. Specially 

 peculiar to the Suctoria are the " sucking-tubes," plasma-rods 

 traversed by a canal, which generally originate far within 

 the cell- body and extract the noimshment from the prey by a 

 pumping movement. In most genera we find only such 

 structures, which can be referred back neither to the cilia of 

 the Ciliata nor to the pseudopodia of the Heliozoa, but are to 

 be regarded as organs sui generis ; from these, in a higher 

 grade of differentiation, have proceeded in the first place 

 those pseudopodium-like tentacles^ and in the second the 

 grasping-threads, which serve only for seizing the prey, and 

 the investigations into the structure of which are not yet con- 

 cluded. In Podophrya gemmipara R. Hertwig ascribes to 

 them a solid structure, while Maupas states that he has found 

 a canal in their interior. 



The latter naturalist has indicated f that nucleoli are at 

 present known only in certain Ciliata and some Suctoria, but 



* L. c. p. 300 et seqq. t L. c. p. 304. 



