466 ACINETA-PARASTTISM. — VORTICELI.TNjE. 



constitute a peculiar tribe of suctorial Animalcules, furnished 

 ■with tubular prolongations which act as suckers. This doctrine of 

 the Acineta-forms, which received for a time very general credence 

 on Prof. Stein's authority, but was strongly contested by others, 

 may now be regarded as finally set aside ; having been based on a 

 misinterpretation of the curious phenomena of ]iarasitism exhibited 

 by these Animalcules, which penetrate the bodies of other Animal- 

 cules, either in their inactive or in their encysted condition, and 

 develope and multiply themselves in their interior. In fig. 20 is 

 seen a Paramecium containing three of these parasites, q, q, q', 

 which work their way into the body without rupturing its integu- 

 ment, pushing this before them so as to form a sort of pouch, 

 wherein they lie, that opens externally in a canal of which the 

 mouth is seen at x, x. The sexual organs of this individual, 

 displaced by the parasites, are shown at a, b. In fig. 19 are seen 

 three Acinetos in different stages of their free state ; one of them, 

 A, being in repose, but putting forth its suctorial appendages ; 

 another, b, undergoing self-division, and having cilia as well as 

 suckers on one-half ; and a third, c, swimming actively in the 

 liquid by means of its cilia. Another parasitic growth, consisting 

 of a large vesicle crowded with Vibrios, has been mistaken by 

 some excellent observers for a spermatic cyst filled with sperma- 

 tozoa. 



349. It is obvious that no Classification of Infusoria can be 



of any permanent value, until it shall have been ascertained by 



the study of their entire life-history what are to be accounted 



really distinct forms ; and the differences between them, consisting 



chiefly in the shape of their bodies, the disposition of their cilia, 



the possession of other locomotive appendages, the position of the 



mouth, the presence of a distinct anal orifice, and the like, are 



matters of such trivial importance as compared with those leading 



features of their structure and physiology on which we have been 



dwelling, that it does not seem desirable to attempt in this place to 



give any account of them. The most remarkable departure from 



the ordinary type is presented by the VorticeUince, the habit of 



which is to attach themselves to the stems of aquatic plants or 



some other supports, either by the apex of their own conical body, 



— as is the case with Stentor (Plate xiv.,fig. 21), one of the largest 



of all Infusoria (being visible to the naked eye), which is very 



common in ponds and ditches, attaching itself to duck -weed, 



decaying reeds, or other floating bodies, round which it forms a 



sort of slimy fringe, but which is often found swimming freely, its 



trumpet-shaped body drawn together into the form of an egg, — 



or by a footstalk several times its own length, as is the case with 



Vorticel/a (Fig. 239), which also occasionally quits its attachment 



(the stalk apparently dying and being thrown-off), and swims 



rapidly through the water, being propelled by the fringe of cilia, 



which, when the body was fixed by its stalk, served to produce 



