THE REPRODUCTION OF THE PROTOZOA 121 



The presence of more than one centriole in a nucleus has led 

 Hartmann (60) to formulate the theory that such nuclei are to be 

 regarded as " polyenergid " nuclei.* Hartmann proposes to dis- 

 tinguish a nucleus with a single centriole as a " monokaryon " from 

 a polyenergid nucleus or " polykaryon " containing many cen- 

 trioles ; he interprets many cases, in which a nucleus appears to 

 become resolved into chromidia from which secondary nuclei are 

 formed, as being really a setting free of monokarya from a complex 

 polykaryon an interpretation which certainly gets over the diffi- 

 culty of the formation 

 of centrioles in second- 

 ary nuclei (see further, 

 p. 255, infra). 



In conclusion, men- 

 tion must be made of 

 the theory of cell-divi- 

 sion and of the causes 

 which bring it about, 

 put forward by Hertwig 

 (91, 92). This theory 

 is based on the sup- 

 position, of which men- 



supra) that for the 



normal performance of FIG. 67. Multiple nuclear division in the male 



Vital functions a cer- sporont of Aggregate jacquemeti. The nucleus, of 



. . which the outline has become irregular but is still 



tain quantitative re- visible, is surrounded by eight centrioles, from 



lation must be main- each of which striations pass towards and into 



j -, A the nucleus. After Moroif (94), magnified 750 



tamed between the ii nea r. 



nuclear substance and 



the cytoplasm. As a standard for the proportion of nuclear 

 mass and cytoplasm (" Kernpl as ma-Norm "), the individual im- 

 mediately after fission may be taken. Exact measurements made 

 on Infusoria show that, while the body grows continuously in size 

 from one division to the next, the nucleus at first diminishes slightly 



* The conception of " energids " is due to Sachs, who coined the term to denote 

 " a single cell-nucleus with the protoplasm governed by it, so that a nucleus and 

 the protoplasm surrounding it are to be conceived of as a whole, and this whole 

 is an organic unity, both in the morphological and the physiological sense." 

 Hertwig (66) has criticized this conception, and has shown its untenability in the 

 case of Protozoa, which behave as single individuals whether they possess one 

 nucleus or many. Hartmann, considering the centriole as the criterion of in- 

 dividuality rather than the nucleus, has revived the energid theory in the manner 

 described above. It leads him to regard an ordinary Metazoan karyokinesis as 

 the division of a polykaryon, in which each separate chromosome represents a 

 distinct nuclear element or monokaryon a conclusion which appears to lead rather 

 to a reductio ad absurdum of the theory. 



