PECULIAR TYPES OP INFUSORIA. 423 



sion of phases whicli any particular type may present, and thus 

 in making a most important extension of our knowledge of its 

 life-history, whilst at the same time eflecting a most desirable 

 reduction in the number of reputed species. Such a study, if 

 perservingly as well as carefully pursued, would be almost certain 

 to lead to the discovery of the true generative process in these 

 creatures, of which we cannot at present be said to know any- 

 thing with certainty. For although an apparent "conjugation" 

 has been observed between the bodies of distinct individuals, 

 both in the ordinary active states of Infusoria, and in their 

 Acineta condition, yet this does not seem truly to represent the 

 sexual union of higher animals ; for the blending of the two in- 

 dividuals is not so complete as to amount to the " fusion" we 

 have seen to occur in previous instances, the boundaries of each 

 remaining distinctly traceable ; and not only two, but three, 

 four, or even more, have been found in continuous union. 



275. It is obvious that no Classification of Infusoria can be ot 

 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 remarka- 

 ble departure from the ordinary type is presented by the Vorti- 

 cellince, 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, 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 ot 

 an egg, — or by a footstalk several times its own length, as is the 

 case with Vorticella (Fig. 196), which also occasionally quits its 

 attachment (the stalk apparently dying and being thrown oft"), 

 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 a vortex in the surrounding fluid, that brought 

 it both food and air. Another curious departure from the ordi- 

 nary type is presented by the family Ophrydinoe ; the animalcules 

 of which, closely resembling some Vorticellinse in their indivi- 

 dual structure, are usually found imbedded in a gelatinous mass, 

 of a greenish color, which is sometimes adherent, sometimes 

 free, and may attain the diameter of four or five inches, pre- 

 senting such a strong general resemblance to a mass of K"ostoe 



