154 
R. T. Young 
mass of nuclei, wliich lack definite nuclear mcmbranes, but possess a 
typical chromatic net-work. Definite »nucleoli« are not evident. Tliere 
is some evidenee here of amitosis, but it is at best inconclusive. But on 
tlie other band tliere is no clear evidenee of de novo formation. Further- 
more, I have not seen a single clear case of mitosis, and yet this is a growing 
region in wliich nuclear multiplication should be at a maximum. The 
relations are certainly very puzzling. 
In the same region of another worm we have, I believe, evidenee 
supporting a de novo theory, for liere one finds a dense syncitium con- 
taining masses of cytoplasm in which nuclear matter if present is evidenc- 
ed only by a few scattered granules; in others therc may be a consider- 
able amount of nuclear matter present but no definitely formed nucleus; 
in others still a definite nucleus with a nuclear reticulum is present. Scat- 
tered among tliese masses, which vary greatly in both shape and size, are 
numerous granules which appear similar to nuclear granules in respcct 
to stain. These can only be accepted with great caution, however, on 
account of the number of food granules here present. Direct division of 
pre-existent nuclei may occur here, but the evidenee of such is inconclusive. 
The nuclear membranes in this worm also are incomplete, apparently 
being represented merely by a specialized part of the nuclear reticulum. 
This I have determined by a careful study of several nuclei. 
While direct division of pre-existent nuclei appears to be somewhat 
more common in this worm, than in those thus far 'discusscd, and 
while it may play a considerable role in nuclear multiplication, my 
evidenee tends to show tliat de novo formation may also occur. The 
relative part played by each is uncertain as yet. 
Mitosis I have not found in any of the 3000 nuclei examined 1 ). 
Thus far we have considered adult Gestodes. We shall now study 
briefly a few larval forms. 
Cysticercus sp. (from Evotomys g. galei). 
(Fig. 14.)- 
I do not find here any sufficient evidenee of de novo formation of 
nuclei. I do find, however, some very interesting evidenee bearing on the 
significance of those denselv staining cells which I have interpreted as 
being composed of nuclear matter thruout. Both in the sub-cuticula 
and parenchyma the nuclei of this worm are densely stained and liomo- 
D See footnote 1), p. 145. 
