CHANGES IN REPRODUCTIVE CELLS OF ELASMOBRANCHS. 289 
As time goes on, the chromosomes assume a more and more 
equatorial position; but their linin filaments remain stretched 
out towards the centrosomes, and form the greater portion of 
an achromatic spindle, the equatorial part of which is con- 
sequently nuclear. 
27. The astral radiations which surround the centrosomes 
become connected with the chromosomes in such a way as to 
clothe the achromatic spindle with a fibrous sheath, structu- 
rally equivalent to that described by Hermann (ante, § 8), 
while even at this early period in the formation of the spindle 
figure, the centrosomes are sometimes divided at the poles 
(figs. 45, 46, c.). 
28. The exact form of the chromosomes, when they appear 
in the monaster of this first heterotype of the second spermato- 
genetic series, varies a good deal from cell to cell; but in the 
majority of cases the loops are at first bent up upon them- 
selves, in the manner represented in figs. 45, 45’. The rod- 
like bodies thus produced at first stand stiffly out from the 
surface of the spindle (fig. 45’), but after a time they flatten 
down in the manner represented in fig. 45. In consequence 
of this, the two limbs of the loop appear in profile to have the 
form of two Greek Q’s place, side by side, and the outer 
surface of the bends being greatly thickened, the original open- 
ing of the loop is reduced between them to the merest slit 
(fig. 45, s.). These thickenings on the outer curves of the Q's 
would appear to correspond with the thickenings on one side 
of the heterotype loop of Salamandra, but in Elasmo- 
branchs they developed equally on both limbs. I was conse- 
quently interested to find that in the great heterotype division 
of the spermatogenesis of newts, these thickenings sometimes 
occur on one, sometimes on both limbs of the elongated loops. 
From the drawings given by Hermann, Flemming, and vom 
Rath, who deal with this form of chromosome in the salaman- 
der, it would appear that the loops are often intentionally repre- 
sented with the plane of their openings at right angles to the 
surface of the spindle, that is, with one limb on and the other 
off the spindle. However this may be, it is certainly rarely if 
