94 



THE ANATOMY OF IXVERTEBRATED ANIMALS. 



usually some other species of Infusorium — when the substance 

 of the latter travels along the interior of the sucker into the 



Fio. 9.—^, Yorticella, active ; B, C, encysted ; Z>, E, F, G, Acinetoe (after Stein). 



body of the Acineta. Solid food is not ingested through these 

 tentacles, so that the Acinetce cannot be fed with indigo or 

 carmine. In the interior of the body there is an endoplast * 

 with one or more contractile vacuoles, and it may be either 

 fixed by a stalk or free. 



The Acinetce multiply by several methods. One of these 

 is simple longitudinal fission, which appears to be rare among 

 them. Another method consists in the development of ciliated 

 embryos in the interior of the body. These embr^^os result 

 from a separation of a portion of the endoplast, and its con- 



soon as the suc'kinor (5isk has bored throncrli the cuticula of the prey, a very- 

 rapid stream, indicated by the fattv particles which it carries, sets along the 

 axis of the tentacle, and, at its base, pours into the rxcighboring part, of the 

 body of the Acineta. . . . The cause of the movement is unknown. It is not, 

 accompanied bv any discernible movement of the walls of the tentacle." 



' No endoplastule, such as exists in other Infusoria^ has been observed as 

 yet in the Acivdoe. Under some circumstances, tlie Acinetm draw in their 

 radiating processes, and surround themselves with a structureless cyst; but 

 this process does not appear to have any relation to either mode of multiplica- 

 tion. 



In Acineta mystacina and Porlopliryafixa, a peculiar mode of multiplication 

 bv division occurs. At the free end of the body a portion becomes constricted 

 off, together with part of the endoplast, from the remaining stalked part. The 

 tentacula are drawn in, and the segment becoming elongated, develops cilia 

 over its whole surface and swims away. 



