Organisms Consisting of One Cell 249 



way, by defining house as a building which must be com- 

 posed of brick or of stone. 



More Detailed Examination of the Anatomy of Higher 



Protozoa 



In behalf of the treatment of reproduction and heredity 

 which will engage us later on, we must now extend our ac- 

 quaintance with the finer structure of some of tlie more 

 highly developed protozoa. Stylonychia, about which some- 

 thing has already been said, may be the first object ul" 

 closer scrutiny. Putter, who has given special attention 

 to the activities of many protista, remarks, "One may take 

 a hypotrichous infusorian (Stylonychia being typical) as an 

 example of the highest complication of body-forai which a 

 single cell is able to reach, for in addition to differentiation 

 into dorsal and ventral sides and the very complicated form 

 of the periphery, we find no less than six different groups of 

 cilia." 23 



Putter's representation of a side view of Stylonychia 

 mytilus, copied in various books and shown in figure 5, illus- 

 trates his statement. He describes in detail the movements 

 of the ciha in crawling; and from all this and from wliat 

 others have written on the subject, it is entirely pi rmisslble 

 to call these main cilia limbs or legs. The elaborate system 

 of fibers connecting and coordinating these limbs will be 

 spoken of in a later section. The statement by Putter about 

 the extent of complication of body possible in a single cell 

 prompts one to wonder, in view of the elaborateness of these 

 animals, whether the limits of possibility of structural dif- 

 ferentiation is much narrower for single-celled than for 

 many-celled animals. In none of the metazoa, exce]>ting the 

 arthropoda and higher vertebrata, do we find a more highly 

 differentiated, and, seemingly, integrated system of loco- 

 motor organs than in Stylonychia and its congeners. 



