242 Robert Thompson Young, 



basis for future investigators in what seems to me a most sug- 

 gestive field for research.^) I believe that the nucleus in these 

 forms is not a morphological, but a physiological en- 

 tity; that the nuclear granules are fundamentally the 

 same as the remaining protoplasm of the cell, but are 

 differentiated therefrom under physiological condi- 

 tions which we do not at present understand; that 

 these granules are perhaps reserve material stored 

 up in the nucleus for future use, the entire cell body 

 being thus occasionally converted into a nucleus; and 

 that the nucleus varies in structure from time to time 

 in response to varying physiological demands made 

 upon it. (The varied pictures presented by the ganglion cells, to 

 which brief reference was made in the discussion of the nervous 

 system, are readily explained by these theories.) Further, if my 

 interpretation of my observations be correct, then distinction 

 between germ and somatic plasm is obviously impos- 

 sible; a special vehicle for the transference of hered- 

 itary qualities is entirely wanting; such qualities 

 must be transmitted by the undifferentiated proto- 

 plasm; cell lineage is manifestly lacking; a mosaic 

 theory is plainly untenable; and the fate of any given 

 embryonic element — whether it shall form paren- 

 chyma, muscle, nerve etc. — must be determined by 

 physiological causes alone. 



Previous to the work of Child (1904) on Moniezia expansa^ 

 there is no record of amitosis in the Cestodes, altho Bugge (1902) 

 has called attention to the lack of mitoses in the development of 

 the flame cells. And the total absence of mitoses in the figures of 

 St. Remy (1901) representing the development ot the oncosphere of 

 Taenia serrata is noticeable. 



But it was Child (1904) who first described amitosis in the 

 Cestodes. A detailed review of his work will not be given here, 

 but attention is called to a few statements which he has made. On 

 p. 548 he says: "Sometimes one or two small bodies stained like 

 the nucleolus may be seen." These "small bodies" I take to be 

 identical with the "nucleolus" except in size. They both correspond 



1) Some of these points have already been suggested by Child (1904). 

 See the discussion of his paper (page 245). 



