184. J. T. CUNNINGHAM. 
Myxine. Moreover, according to Jensen, in Triopa the filament 
is formed first before the sperm-nucleus is differentiated, and 
has a definite existence apart from the drops of plasma. 
According to my observations in Myxine there is no indication 
of a filament as a distinct structure at all ; the sperm-nuclei are 
differentiated within the spermatocyte, and then the cell-plasma 
is merely drawn out into viscous threads which form the tails 
of the spermatozoa. 
But although I have compared the multinuclear spermato- 
cyte of Triopa with that of Myxine, I cannot regard them as 
morphologically homologous. As I have stated above, I believe 
that a considerable portion of the spindle-shaped cells in 
Myxine remains unused after the separation of the spermatozoa, 
and represents the blastophore or cytophore in other cases. In 
Triopa, on the contrary, the cytophore is separated before the 
spermatocytes of Jensen’s nomenclature are constituted, and 
the whole of the protoplasm of these spermatocytes is used up 
in the formation of the spermatozoa. In comparing the testi- 
cular cells of Myxine with those of Molluscs either the whole 
contents of a follicle must be regarded as the equivalent of a 
single spermatogemma or sperm-polyplast, or each of my 
spermatocytes must be regarded as that equivalent. The 
former hypothesis seems to me untenable, because in the 
multiplication of the spermatic cells in the follicle there is no 
indication of anything corresponding to a cytophore or “ blasto- 
phoral corpuscle.” On the other hand, after the separation of 
the spermatozoa from each spermatocyte there is a blastophoral 
remnant left behind. 
It must, therefore, be understood that I have used the term 
spermatocyte in its etymological sense, and that the element 
thus designated in Myxine corresponds, not, as Nansen sup- 
posed, to a cell which is bodily transformed by change of 
structure into a single spermatozoon, but to what in other cases 
has been called a spermatogonium or spermatospore, which gives 
rise to a bundle of spermatozoa. 
It is interesting to note the extreme simplicity of the struc- 
ture and development of the testicular follicles in Myxine, a 
