188 VniversHy of California Publications in Zoology [Vol. 16 



tiated nuclei of the Ciliata and the other resulting in the metazoan 

 nucleus and centrosome. 



Closely connected with these theories are two other conceptions 

 first formulated by R. Hertwig in 1902-03, as the chromidial hy- 

 pothesis and the nucleo-cytoplasmic ratio. The latter is the more 

 important generalization, and has been far-reaching in its scope, 

 spreading widely in Ww domain of metazoan as well as protozoan 

 cytology. 



Briefly stated it may be given thus: The normal continuance of 

 the vital functions of a cell is dependent upon a certain quantitative 

 relation of nucleus and cytoplasm. Any disturbance of this ratio, as, 

 for example, an increase in the nuclear size without a corresponding 

 cytoplasmic growth, leads to degeneration and death. The extrusion 

 of chromidia from the nucleus may be one means of preserving this 

 ratio. 



The chromidial hypothesis was closely interwoven with his nucleo- 

 cytoplasmic ratio, but it received its fullest amplification at the hands 

 of Goldsehmidt (1904-1905), and Schaudinn (1896-1903). 



Goldsehmidt, from his work on nematodes and Protozoa, came to 

 the conclusion that every cell is primarily binucleate, containing a 

 somatic and a generative nucleus. These may be united into a single 

 structure, the amphinucleus, or may be completely separated, as in 

 the ciliates. A separation may also take place by the formation of 

 chromidia at the time of gametogeuesis. This view has led to the 

 homologizing of widely different structures in both metazoan and 

 protozoan cells, much of which, in the opinion of Dobell (1909), 

 "greatly exceed the limits of legitimate inference." 



Building on this foundation, Schaudinn (1896-1903) worked out 

 a theory of binuelearity which differs somewhat from the earlier views. 

 The occurrence of a typical centrosome in the Heliozoa led him to the 

 conception of its origin from a second cell nucleus which became 

 differentiated early in the phylogenetic history of the Protozoa. The 

 earliest forms in this evolutionary transformation would be that in 

 which two nuclei of equal value were present, and this condition he 

 found in Amoeba binucleata, with its two nuclei equal in structure 

 and function, which divide by a primitive mitosis. He says, however, 

 that "Zugleich scheint an den flachen Polen die Membran sich etwas 

 zu verdieken, so dass es hier, wie bei Actinosphaerium, schon auf so 

 friihem Stadium zur Ausbildung des sogenannten Polplatten kommt 

 die Function der hier fehlenden Centrosomen mit ihren Strahlen- 



