SEGMENTATION AND DIFFERENTIATION OF CHROMOSOMES. 289 
gained by tbeir smaller size. The best examples are to be 
obtained from the still further shortened chi-omosomes of the 
daughter-plates. This is shown in fig. 7 of my former paper.^ 
'L’he whole series of chromosomes from this nucleus is shown 
here in fig. 16 a. 
Figs. 10-12 are spermatogonia! daughter-plates, and a 
transverse joint is very clear in many of the chromosomes, 
especially in the smaller ones. 
Attention has already been drawn to the fact that the 
transverse joint often divides the chromosome into two very 
unequal segments, and also that the apices of the V^s of the 
longer chromosomes correspond with the transverse joints of 
the shorter ones. Special regard should be paid to figs. 10 
and 11 and 15 a in this respect. In all of these it is seen that 
the two longest chi’omosomes form V’s with approximately 
equal limbs, while those next in size have very unequal 
limbs. As we follow down the series of chromosomes the 
V’s gradually pass into dumb-bells in the shortest ones. 
Meiotic Phase. 
The development and fate of the transverse constrictions of 
the ineiotic chromosomes was fully described in my former 
paper. Here it is only necessary to recall that there emerges 
from the synizetic mass the full number of long chromosomes, 
which become spaced out through the nucleus during dia- 
kinesis. At first (i.e. while they are still long) they are nn- 
segmented, but as they shorten up the transverse consti'ictions 
appear. Finally they become more or less dumb-bell or hour- 
glass shaped, and then pair to form the typical ineiotic 
tetrads. 
It is unnecessary to describe the development of the trans- 
verse constrictions again here, so I have started with the 
fully formed tetrads. A complete series of these, from a cell 
' In the explanation of the figures, and on p. 26 of that paiier, this 
figure is refeived to as an equatorial plate. This is a slip, and it is 
correctly described as a daughter-plate on p. 22. 
VOL. 58, EAUT 2. NEW SERIES. 
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