76 SUMMAKY OF CUERENT RESEARCHES RELATING TO 



minates anteriorly in a slightly developed conical neck, at the ex- 

 tremity of which there is an aperture. The body is clothed with a thick 

 cuticular membrane, and this presents spirally arranged longitudinal 

 folds. The neck, covered with a thin cuticle, is alone contractile ; at 

 the will of the animal it can invaginate itself in the interior. At the 

 base of the neck there is a collar of long cilia, by means of which the 

 animal can execute two kinds of movements ; one slow, as if the 

 animal were creeping over various objects ; the others are sudden 

 rapid leaps. The cilia are about as long as the body, stout, rigid, 

 and arranged in three circles placed one above the other ; each circle 

 contains seven or eight cilia, so that the entire collar consists of from 

 twenty-one to twenty-four. A nucleus and a contractile vacuole are 

 present. 



The most interesting point in the organization of this animal is 

 the constant presence of four suckers, arranged symmetrically upon 

 the margin of the orifice of the neck. They are very short, not so 

 long as the neck ; and in structure are the same as the suckers of the 

 Acinetina. When the neck becomes invaginated, the suckers are like- 

 wise carried into the interior, and cannot then be observed. It is this 

 position that the animal usually presents, and it is then easily mis- 

 taken for a ciliated Infusorian. Sometimes the animal fixes itself, by 

 means of its suckers, to various objects ; or it may creep slowly by the 

 aid of its cilia, with the mouth open and the suckers directed forward. 

 This Infusorian was first found by Cohn, who gave a very super- 

 ficial description of it under the name of A carella siro. The essential 

 character of the presence of the four suckers, as well as several other 

 chai-acters, escaped him ; and this led him to place it among the 

 Ciliata. As, however, by some of its characters it is a ciliated Infu- 

 sorian, and by others an Acinetine, it is necessary to form for it, at 

 least, a distinct family, which the author proposes to name Suctociliata. 

 This family may be arbitrarily arranged in either of the orders as an 

 intermediate form ; or, if it be j)referred, as a new order Suctociliata. 

 It remains to be learned whether the Suctociliata are not ancient 

 primitive forms which may have given origin, on the one hand, to the 

 Ciliata, by the disappearance of the suckers, and, on the other, to 

 the Acinetina, by the suppression of the vibratile cilia ; or should we 

 not rather regard Acarella siro as a Ciliate which has acquired suckers 

 without having any genealogical relations with the Acinetina ? or, 

 lastly, as an Acinetine which may have retained its embryonic cilia 

 until its adult age ? We cannot choose any one of these three 

 suppositions as being the most probable, all three of them having 

 considerations in their favour. The developmental history of the 

 Infusorian, which is very difficult to study on account of its rapid 

 movements, can alone decide the matter with certainty. The last of 

 the suppositions, however, seems the least probable. 



M. E, Maupas adversely criticizes* Mereschkowsky's views, 



pointing out that Stein's Adinoholus varians is a better intermediate 



form, and that the author is in error in saying that the Acinetidae 



have vibratile cilia only in their embryonic state, as some PodojjJirycB 



* Comptes Rendus, xcv. (1882) pp. 13S1-4. 



