The Somatic Nuclei of Certain Cestodes. 
159 
plication apparently plays a considerable part. As I have previously 
noted in this paper 1 ) it is very difficult to sav whether these apparent 
cases are actually such or not, all depending ultimatelv on the origin 
of the new »nucleolus «, the essential part of the nucleus, whether by 
division or de novo. I consider it probable, however, that in many cases 
at least we have the occurrence of a true division process. In the ma- 
jority of instances, however, this appears to have given way to de novo 
formation. 
The evidence for this latter process is not as yet absolutely con- 
clusive. Still this theory will satisfy, I believe, more nearlv than any 
other, the requirements of the observed facts, which summarized are 
as follows: 
1. The occurrence of masses of granulär protoplasm lacking any 
evident nuclei. 
2. The occurrence of isolated »nucleoli« of varving size from 1 / i 
to 1 micron in diameter, which are usually found in the above mentioned 
masses of protoplasm but occasionally lie free in the parenchyma Strands. 
3. The occasional occurrence of nuelear membranes in these proto- 
plasmic masses, containing no apparent nuelear matter. 
4. The occurrence in the anlagen of the genital ducts of great var- 
iations in shape, size, nuelear content and membranes of the develop- 
ing nuclei. 
5. The comparative raritv of dividing nuclei in many regions of ap- 
parently active nuelear multiplication. If numerous nuclei in an ac- 
tively growing tissue were arising by division of pre-existent nuclei, it is 
Strange at least that more evidence of such division should not be found. 
6. The marked variations in staining density between adjacent 
cells. That the densely stained cells are something more than mere 
aggregations of protoplasm is clearly shown, I believe, by my micro- 
chemical tests on Taenia crassicollis, in which the staining matter in 
these cells behaves as a nucleo-albumin in response to the reagents em- 
ployed. That this material, however, does not, as I supposed in Cysti- 
cercus pisiformis (1. c., p. 242), make up the entire cell body, but is 
rather deposited in the latter, is indicated by the tests with 50% hydro- 
chloric acid and 1 % potassium hydrate, which brought out most clearly 
the distinction between cell body and deposited nuelear substance. It 
is probably significant that the densely stained cells are most numerous 
in the sub-cuticula where thev can receive soonest absorbed nutriment 
*) See p. 144. 
