204 Dr. L. Plate on the Genus Acinetoides. 



quently only for a few minutes. Shortly before the separa- 

 tion the cilia begin to work more vigorously, the animal 

 moves a little to and fro, nay, it sometimes rotates around 

 the sucking-tube, which is still inserted in the prey, and 

 finally separates entirely from its victim. Its movements 

 while swimming freely about are very irregular and exactly 

 resemble the spasmodic movements of the buds of Acinetse. 

 I have frequently observed that within about a minute of 

 their separation the animalcules had attached themselves 

 again. 



Acinetoides Oreeffii is so large that only two individuals 

 can find room at the same time upon a Zoothamnium^ as the 

 species always selects the base of the bell for fixation. It is 

 otherwise, however, with the smaller species. This avoids 

 the neighbourhood of the peduncle and attaches itself by 

 preference to the peristomial region or the sides of the body ; 

 and in consequence of its small size we often see from three 

 to five individuals occupied at the same time in sucking out 

 the same Zooihamnium. The death of the latter occurs very 

 soon after the attachment of an Acinetoides, so that this 

 evidently brings its prey in contact with some corrosive fluid. 

 The loss of substance which the Zoothamnium thus suffers 

 causes the collapse of the anterior part of the bell, the cuticle 

 of which falls into numerous wrinkles and folds. It is 

 remarkable that the animalcules never completely exhaust 

 their victims (even when several of them prey upon the same 

 individual), but they confine themselves to a portion of the 

 plasma and then fall upon another Infusorian. The only 

 probable reason of this is that the body-substance of the 

 Zoothamnium is altered by long action of the destructive 

 fluid secreted by the Acineta, and then no longer suits the 

 taste of our animalcules. 



As to the reproduction of the genus Acinetoides, I could 

 learn nothing except from the smaller species. Of course a 

 thorough knowledge of this is of the greatest importance, 

 seeing that without it there is always a possibility that the 

 Protozoa described are only swarm-buds of other Suctoria, aa 

 they are distinguished from these only by the presence of a 

 single sucking-tube. That such a supposition was incorrect 

 was indeed quite clear to me from the first, as I always ob- 

 served the Acinetoides in great numbers together, and on the 

 colonies of Zoothamnium attacked by them there were in 

 addition only a few Podophryce, which were smaller than the 

 Suctoria here described, and therefore could not possibly be 

 connected with them. Moreover the swarming-buds of these 

 Podophryce also occurred j they had quite a different form of 



