CHANGES IN REPRODUCTIVE CELLS OF ELASMOBRANCHS. 287 
also described by Hermanu! in the prophasis of the great 
heterotype division of the spermatogenesis in Salamandra. 
These monilations in Elasmobranchs, however, do not consist 
of one large microsome, as Hermann’s figure would lead one 
to expect, but are each formed by a group of numerous chro- 
matic granules,and these are embedded in a scaffolding of linin. 
Delicate connecting filaments of this substance spread from 
the monilations on the threads in all directions. The polarised 
threadwork is disposed throughout the nucleus in long parallel 
loops (figs. 37, 38), the free ends of which, if they exist, 
are difficult to discern. After a time the threads begin to 
show longitudinal splitting (figs. 38, 40), and the double ropes 
thus formed, dividing into equal segments, eventually give rise 
to twelve thick loops which (fig. 42) form the twelve ring 
chromosomes (fig. 43) typical of the divisions of the second 
spermatogenetic period. 
24. There are thus, after the rest of transformation, only half 
as many chromosomes, 1. e. separate chromatic masses, as there 
were before, and the halving of their number, being brought 
about while the nuclei are still at rest, is to that extent 
comparable to what is now known to go forward during the 
maturation of the reproductive elements of plants. I there- 
fore propose the term Synaptic phase® to denote the period at 
which this most important change appears in the morphological 
character of reproductive cells. 
25. Concomitantly with the formation of the twelve ring 
chromosomes, the centrosomes (figs. 40, 41, c.) begin to separate, 
and their greatly enlarged archoplasmic envelope (Nebenkern) 
(fig. 41,a@.) is drawn out between them into a little archoplasmic 
spindle (fig. 42), strictly comparable to that described by Her- 
mann during the division of the spermatocytes of Salamandra. 
As in the divisions of the previous spermatogenetic period, 
the separation of the centrosomes occurs with great rapidity, 
the archoplasm being drawn asunder into two parts (figs. 43 
and 44), although it sometimes presents the appearance of a 
? Loc. cit. 
* Gr, cvvarrw, to fuse together. 
vou. 38, PART 2,—-NEW SER. T 
