

70 Miscellaneous. 



In size it does not exceed a small Halteria ; its body, which is 

 rounded and somewhat pyriform, terminates anteriorly in a slightly 

 developed conical neck, at the extremity of which there is an aper- 

 ture. The body is clothed with a thick cuticular membrane, espe- 

 cially at the posterior extremity ; and this presents spirally arranged 

 longitudinal folds. This membrane, by its resistancy, determines the 

 general form of the body. The neck, covered with a thin cuticle, 

 is alone contractile ; at the will of the animal it can invaginate itself 

 in the interior, and thus become elongated and shortened. However, 

 in its state of greatest extension it never exceeds the length of the 



body. 



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 

 kind consists of slow movements, as if the animal were creeping over 

 various objects ; the others are sudden leaps, so rapid that it is im- 

 possible to follow the Infusorian. The cilia are about as long as the 

 body, stout, rigid, and arranged in three circles placed one above 

 the other ; the cilia of the middle circle are perpendicular to the 

 long axis of the animal ; those of the other two circles are directed 

 obliquely, those of the anterior circle towards the anterior extre- 

 mity, and those of the posterior circle towards the posterior extre- 

 mity. Each circle contains seven or eight cilia, so that the entire 

 collar consists of from twenty-one to twenty-four. • 



The granular and colourless protoplasm encloses a rounded or 

 slightly oval nucleus, situated at the middle of the body, and a con- 

 tractile vacuole placed at the posterior extremity. 



The most interesting point in the organization of tKis animal is 

 the constant presence of four suckers, arranged symmetrically upon 

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

 attaining even the length of the neck : as to their structure, it is 

 the same as that of the suckers of the Acinetina ; we distinguish in 

 them a slender peduncle, terminated at the extremity by a globu- 

 lar enlargement. When the heck becomes invaginated, the four 

 suckers are likewise carried into the interior, and carfhot then be 

 observed. It is this position that the animal usually presents, and 

 it is then easily mistaken for a ciliated Infusorian. 



When it traverses the field of the microscope by sudden leaps, it 

 always presents this aspect ; often it even retains the same appear- 

 ance immediately after stopping; but when it is observed for a 

 certain length of time we see the neck become devaginated, and 

 the four suckers make cheir appearance. When startled by a shock, 

 if the Infusorian wishes to leap, it passes them again into the inte- 

 rior. 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. 



The Infusorian, the organization of which I have just described in 

 some detail, was detected long ago by a German naturalist, M.Cohn, 



who has given a very superficial description of it under the name of 

 AcareTla siro. The essential character of the presence of the four 





