SPERMATOGENESIS IN MYXINE GLUTINOSA. 177 
successive steps in the transformation of the nucleus of the 
spermatocyte into a number of sperm-nuclei. I believe, how- 
ever, that d,e, and c, Pl. IV, fig. 11, exhibit stages in this 
process; d and e are spermatocytes with two and three nuclei 
respectively, and it seems that the original nucleus of the 
spermatocyte simply divides without any process of karyo- 
kinesis into first two, and then more, smaller resting nuclei. 
The chromatin in these small nuclei then undergoes concentra- 
tion to form the solid sperm-nuclei, all other parts of the 
nucleus disappearing. If the membrane of the resting nucleus 
is chromatin, it must, of course, cease to exist as a membrane 
after the concentration, while the achromatic substance (Kern- 
saft) doubtless fuses with the cell-plasma. In this way the 
spermatocyte reaches the condition seen in ¢, fig. 11, or fig. 1. 
Another point on which I am uncertain is the history of the 
capsules after the spermatozoa have been discharged from 
them. I think there is little reason to suppose that a given 
capsule can produce more than one crop of spermatozoa. The 
capsules closely resemble the follicle of the ovary, and we know 
that the follicles are gradually atrophied after the discharge of 
their ova. But some of the follicles of the ripe testis contain 
a large number of small separate cells whose nuclei are in the 
resting condition ; cells from such a follicle are represented in 
P]. IV, fig. 10. Similar small cells are also often seen in 
addition to the other elements in a follicle which contains ripe 
spermatozoa. Since these cells are considerably smaller than 
the spindle-shaped cells from which the spermatozoa are derived, 
I cannot believe, as Dr. Nansen does, that they have anything 
to do with the production of the spermatozoa. It seems to me 
much more likely that they are derived from the remnants of 
the spindle-shaped cells left after the spermatozoa have been 
formed, and that capsules containing them are in process of 
degeneration. 
In my former paper (2) on the reproductive elements of 
Myxine I gave the following description of the spermatozoa 
and their genesis :—‘‘ The spermatozoa possess a pear-shaped 
head which is very highly refringent, and has a distinct out- 
VOL. XXXII], PART I.—NEW SER. M 
