THE FUNDAMENTAL ORGANIZATION 75 



particularly in the early sporozoites of Monocystis, Horning was 

 unable to demonstrate the presence of mitochondria and concluded 

 that they are absent in young forms but make their appearance in 

 the process of development. This was interpreted as evidence of 

 their origin de novo in the cytoplasm (Horning, 1929). 



Suspicions have been aroused from time to time as to the nuclear 

 origin of mitochondria, although little positive evidence has been 

 forthcoming. Some has been obtained recently, however, in con- 

 nection with observations on the reorganization processes following 

 conjugation of Uroleptus halseyi (Calkins, 1930). Here the old 

 macronuclei, eight in number, break up, each into a group of minute 

 spherules. These spherules, at first, have a deeply staining cortex 



* ft ." ■■ - » ft 



IT: 



m 







• &f^ii *^r,*f 



f. #•--* V- • A» ^>« 51 



' *V.**YAk a' *« * *** •* 



Fig. 38. — Dividing mitochondria in Opalina. (After Richardson and Horning, Jour. 

 Morph., courtesy of Wistar Institute.) 



(with iron hematoxylin) and a more feebly staining medullary por- 

 tion, thus giving the appearance of black rings in optical section. 

 At a later stage the apparent rings break up into small crescents 

 and the latter ultimately become rod-like mitochondria filling the 

 cell of the ex-con jugant (Fig. 37) . 



Opinions are equally divergent regarding the functions of mito- 

 chondria in the cell. The earliest suggestion was that of Faure- 

 Fremiet (1910), who believed that they play some part in connection 

 with the preparation of germ cells, and who was influenced no 

 doubt, by their conspicuous presence in germ cells of Metazoa. 

 Confirmation of this suggestion is furnished in part by observations 

 of Zweibaum (1922), who observed an increase in the fatty acid 

 content of Paramecium when ready to conjugate; and confirmed, 



