CELL MULTIPLICATION IN SUB-CUTICULA. 393 



develop to complete nuclei in situ. Young bases his theory of 

 the independent origin of granules from a cytogenic protoplasmic 

 mass upon the following facts: 



1. The occurrence of masses of granular protoplasm lacking 

 any evident nuclei. 



2. The occurrence of isolated " nucleoli" of varying size from 

 34 to i micron in diameter, which are usually found in the above 

 mentioned masses of protoplasm but occasionally lie free in the 

 parenchyma strands. 



I believe, however, that these facts may be equally well ac- 

 counted for by assuming the extrusion of chromidia from a 

 mother nucleus. Masses of granular protoplasm without any 

 evident nuclei, which occur but rarely may be explained as having 

 been severed from parent masses after impregnation \vith 

 chromidia. The occurrence of isolated "nucleoli" can be ac- 

 counted for just as well by assuming the migration of chromidia 

 from the nuclei along the strands of the cytoplasmic network, 

 as by the assumption of their development from the protoplasm 

 in situ. 



Young, in a later paper ('13) dealing with gametogenesis, in 

 Tcenia pisiformis says (p. 375): "I believe that new nuclei arise 

 either from chromidial extrusions from old nuclei, or 'de novo' in 

 the cytoplasm. . . . The structure of the nucleus a loose 

 collection of chromatin bodies without a membrane renders 

 the extrusion of chromidia an easy matter. After their extrusion 

 new chromatin is added and that part of the cell containing them 

 is constricted off, to give rise in its turn to other cells. ... It is 

 obviously impossible to say, however, whether any chromatin 

 granule in the cytoplasm is a chromidial extrusion or a 'de novo' 

 formation." 



Since I have seen these very small granules, all of about the 

 same size, present in the nuclear membrane as though impeded 

 by it in their exit, along the strands of the protoplasmic network, 

 from the nucleus to the cytoplasm, I believe that these granules 

 are extruded from the mother nucleus. Moreover, since I have 

 observed granules of various shapes and sizes, many of the 

 larger ones appearing to be composed of three or four smaller 

 ones partly united, and since I have often seen a number of 



