238 Robert Thompson Young, 



separate later, instead of each one having- its own individnal mem- 

 brane developed at the outset. 



If my theory be correct, then the nucleoplasm is, funda- 

 mentally, the same as the cytoplasm, and is differentiated 

 from the latter under conditions not at present understood, but 

 which are probably entirely physiological in character. It is possible 

 that the nuclear granules are merely condensed masses of 

 undifferentiated protoplasm, chemically the same as the remaining 

 protoplasm of the cell and differing from the latter only in density. 

 The fact that a clear zone usually surrounds the developing granule 

 speaks for the probability of the formation of the latter by the 

 condensation of the protoplasmic granules in a given area. The 

 development of the basal plate and ciliate process from granules which 

 in every way appear similar to the other granules in the nucleus, 

 the formation of a nuclear membrane by a condensation of proto- 

 plasmic granules and the frequent occurrence of such granules on 

 the membrane are all facts which speak for the essentially simple 

 protoplasmic character of these granules. But their constant occurrence 

 in the nucleus indicates that they have a definite and important 

 function to fulfil and that they are, to some extent at least, different 

 from the remaining protoplasm. In sections of the scolex of Taenia 

 serrata stained in Heidenhain's haematoxylin, wasserblau and picric 

 acid, I have found dense masses of protoplasm whose structure lends 

 ground to the belief that the nuclear granules are something more 

 than mere protoplasmic condensations (see Fig. 8). I have not been 

 able to establish positively their identitj-, but that they are cellular 

 elements and not mere artifacts is proven by the fact that they 

 contain developing nuclei, the granules of which are stained black 

 or dark brown by the haematoxylin while the cytoplasm is 

 stained blue by the wasserblau. These masses are very dense and 

 it seems probable that if mere condensation of protoplasm were 

 sufficient to account for the dai'k nuclear stain, then these masses 

 would take some of the nuclear stain — the haematox3din. But, 

 excepting the nuclear granules, such is not the case. They are 

 stained intensely blue without showing a trace of the haematoxylin. 

 What is the source of the nuclear membrane? It is differen- 

 tiated from the original granular cytoplasm. In Fig. 4 is re- 

 presented a developing cell. In this figure the nuclear membrane is 

 clearly shown on one side of the cell as a distinct, darkl}'- stained 

 border, which gradually merges in either direction into the un- 



