424 
R. T. Young 
The skein (“synapsis”?) stage of what may, for convenience sake be 
termed primary spermatocytes is easily identified, but in later stages of 
niitosis. I cannot always determine with certainty the order of cells to 
whicli they belong. 
d) Fragmentation of first, and formation of second gpermato- 
cytes (spermatids). 
There now ensues what I have described previously (1913) as de- 
generation of mitosis, and which constitutes the principal evidence for 
my view. Following the development of skeins in the cytophores, the 
former, in most cases at least, do not give rise to chromosomes and undergo 
the succeeding stages of mitosis, but become scattered as fragments thru 
the cytophore, and it apparently is from these fragments that a new 
generation of cells, which may for convenience be called secondary sper- 
matocytes, arise (figs. 8, 9, 10 and 15). 
Here again I cannot speak with absolute certainty. All that I know 
is that succeeding, or coincident with, the dispersal of the skein fragments 
thru the cytophore, the secondary spermatocytes arise, without, in most 
cases at least, any successful mitosis of the primary spermatocytes. The 
most natural Interpretation is that above given. 
This fragmentation of skeins I have repeatedly observed in fixed 
material from several species, and while I have not been able to follow 
their actual dispersion thru the cytophore in living material, I have seen 
the fragments scattered in cytophores, or parts of cytophores, in such 
material from Rhyncobothrium bulbifer. 
The question may arise as to the possibility of the intervention of 
mitoses between the stages described, and tljeir escape from observation. 
I believe I have guarded against this possibility by sectioning all the 
proglottids of several wornis thni the region where these stages were 
occurring, so that it is scarcely likely that any intermediate and unsuspected 
stages have escaped my notice. Furthermore sperm development takes 
place very rapidly. In several species I have observed that the testes in 
one proglottid showed no signs of sperm, while two or three proglottids 
posterior thereto the latter were present in great numbers. 
A similar process of nuclear fragmentation and origin of secondary 
nuclei from chromatin fragments has been described by Child (1907, II) 
in Moniezia, and by Gough (1909) in Stilesia. while Stevens (1907) sugges- 
ted, and Griggs(1909) later claimed its occurrence inSynchytrium. IVhile 
I have no personal acqaintance with this fungus, the descriptions and 
figures of these authors strongly suggest a similarity of the process here 
