LOCOMOTIVE AND PREHENSILE APPENDAGES. 65 



form constitute a hair-like caudal termination in the genera Uronema and 

 Urotricha. "Styles" and "stylate appendages," differing from the organs 

 referred to the last-named category in their greater comparative bulk and 

 thickness, are most abundantly represented among the Hypotrichous sub- 

 order of the Ciliata, being developed in well-defined groups or series on the 

 ventral aspect of such genera as OxytricJia and Stylonychia, and being 

 represented as a single terminal caudal style among the members of the 

 family Dysteriadae. Of uncini, which also occur chiefly among the 

 Oxytrichidje, it may be said that, except for their usually shorter and 

 curved or claw-like shape, they coincide entirely in character and function 

 with the ordinary stylate structures, and act in combination with them as 

 most efficient ambulatory organs. It is undoubtedly among the members 

 of this family group that the cilia attain their highest and most luxuriant 

 development, in many species all of the four typical variations of these 

 appendages being borne by a single individual. Here, too, in certain 

 species, such as StylonycJiia ptcstnlata, S. mytilus, and Eiiplotes patella, 

 we find the styles and setae departing altogether from their ordinarily 

 simple character, and assuming a more or less branched and often elegantly 

 feathered or fimbriate character. Furthermore, as recently pointed out by 

 Sterki, the adoral series of cilia among these Infusoria differ considerably 

 from vibratile cilia of the ordinary type. These modified cilia are much 

 flattened or compressed, and appropriately receive from him the distinc- 

 tive title of " membranell^." 



In addition to the cilia and their various modifications as above enume- 

 rated, there have to be included in the list of locomotive and prehensile 

 appendages now under consideration, the diverse forms of membranes, 

 some vibratory or undulating and others quiescent, which, either as isolated 

 structures or in combination with cilia or flagella, compass or assist in com- 

 passing the objects more usually relegated exclusively to one or other of 

 these last-named structures. As has been previously submitted (see p. i^), 

 an undulating membrane may be regarded from a developmental aspect as 

 the root or primal form only of the adoral fringe of cilia ; in certain other 

 directions, however, it develops an entirely independent type of structure. 

 Commencing with the lowly organized Trypanosomata, where it is found 

 to constitute the sole organ of progression, it makes its next appearance 

 as a supplementary locomotive organ in the Flagellate genera Trichomonas 

 and certain species of Hexamita. By far the most remarkable development 

 of a membraniform appendage in connection with the Flagellate section of 

 the Infusoria, is undoubtedly represented by the singular infundibular mem- 

 branous expansion or " collar," with its characteristic circulating currents, 

 distinctive of the order here distinguished by the title of the Choano- 

 Flagellata, and met with elsewhere throughout the entire organic series 

 only in association with the class Spongida, whose intimate relationship 

 with these Flagellata is thus indubitably established. The marvellous 

 mechanism of this collar-like membrane, and its utility in combination with 



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