The Somatic Nuclei of Certain Cestodes. 
147 
these »nucleoli«. This evidence is not positive, however, and the occur- 
rence of evidently immature nuclei in protoplasmic masses, which 
are unconnected with other siraiiar masses, save by the general paren- 
chyma Strands, argues strongly for their independent origin in these 
masses. 
The aidagen of the genital ducts are a mass of closely packed nuclei 
embedded in a granulo-fibrillar protoplasm where very active nuclear 
multiplication is undoubtedly occurring. The nuclei are mostlv very 
irregulär in shape, vary as much as 100% in size, and present marked 
differences in densitv, form of chromatin content and presence or ab- 
sence of nuclear membranes. Some nuclei are merely densely stained 
aggregations of chromatin, others show distinct »nucleoli« and nuclear 
membranes, others possess the latter, but not the former, while some 
masses of protoplasm show no evidence of nuclear structure whatever. 
The determination of the method of nuclear increase in this tissue 
presents great difficulties. The marked variations in nuclear structure 
strongly suggest a de novo formation. On the other hand the occur- 
rence of many possible cases of nuclear fission render it probable that 
this method mav also plav a considerable part. 
Outside of the genital ducts I find occasional evidence of nuclear 
fission, but these cases are rare, and while I believe that such a method 
of nuclear increase occasionally occurs, I consider it the exception rather 
than the rule. 
I have found no instances of mitosis in this worm in more than 3000 
nuclei examined 1 ). 
Nuclear differences are found in this material similar to those de- 
scribed in Moniezia. In preparations stained with safranin and wasser- 
blau these differences are particularly well shown. In some cases the 
nucleus stains uniformily (or approximately so) in the safranin, other 
nuclei have indefinite chromatic bodies, while in others still there is a 
definite »nucleolus« and nuclear membrane. 
The latter is tvpically incomplete in Thysanosoma as in Moniezia. 
Careful focussing with high powers shows it to consist merely of heavily 
stained Strands of protoplasm surrounding the nucleus, which do not, 
in many cases at least, form a continuous membrane, but leave many 
open spaces between each other even tho the membrane on ordinary 
inspection appears to be complete. Small masses of chromatin are 
often found in intimate union with the membrane and both doubtless 
10 k 
See footnote 1), p. 145. 
