SPERMATOGENESIS IN MYXINE GLUTINOSA. 179 
subdivide, becoming still smaller; when subdivision ceases 
they become spermatides. By an elongation of the nucleus, as 
well as the whole body of the cell, these spermatides are now 
gradually transformed into ripe spermatozoa. Concerning the 
manner of this transformation Dr. Nansen writes :—‘‘ As to 
the details of the development of the spermatides into sper- 
matozoa, I will give no circumstantial description here; my 
investigations of that branch of the subject are not yet 
finished. From the little I have seen I think, however, that 
the spermatozoon is formed from the nucleus as well as from 
the protoplasm of the spermatide, i. e. the whole spermatide is 
transformed into a spermatozoon. As to the tail, that is 
perhaps formed partly by an elongation of the nucleus, partly 
by the protoplasm of the spermatide.”’ 
Thus the spindle-shaped cells which I have described are, 
according to Nansen, stages in the transformation of a single 
spermatide into a spermatozoon. There is no difference 
between us as to the elements seen in the testis of Myxine, but 
only as to their interpretation. But although the elements 
I have described are recognisable in Nansen’s figures, they 
are not accurately represented. He figures the slightly more 
deeply stained core of the spindle-shaped cell as the nucleus, 
and supposes that this becomes the head of the spermatozoon. 
The true sperm-nuclei figured by me in the interior of the 
spindles are nowhere figured by Nansen. This error vitiates 
entirely his figures and description. ‘Two obvious difficulties 
in his interpretation he does not notice. One is that the 
spindle-shaped spermatides even in his own figures have a 
filamentous process at each end ; if one of these is the tail of 
the spermatozoon what becomes of the other? ‘The second 
difficulty is the enormously greater size of the spindle-shaped 
cells as compared with the spermatozoon. How could one of 
the former dwindle away to the dimensions of one of the latter ? 
This difference in size is of course a necessary consequence of 
the mode of formation of spermatozoa which I have described. 
There are two other points, both discussed in Dr. Nansen’s 
paper, to which I have given some attention. One is the 
