124 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
reéxamination will show that a similar arrangement of the spireme 
threads occurs in many forms where it has not hitherto been described. 
Even in the Orthoptera, where the polarity is in general well marked, 
there is great variation in this respect in different species, and in some 
cases might easily be overlooked, as it seems to have been by McClung 
and Sutton. 
Farmer and Moore (:05) emphasize the fact that there are always 
two distinct stages of the polar loops, which they have termed the first 
and second contraction figures. According to these authors, during 
the early growth period the spireme assumes the form of polar loops, 
which are always one-half as numerous as somatic chromosomes. 
‘‘At the same time, the whole chromatic network contracts away from 
the nuclear membrane, this change producing the First Contraction 
figure. As time goes on the loops become not only increasingly 
chromatic but also opened out again, until the apparent polarisation is 
more or less completely lost and the nuclei present the well-known 
coarse spirem figure within the strands of which double beading 
or actual longitudinal fission is always more or less apparent. ‘The 
coarse spirem figure often constitutes a prolonged phase, but it is in 
all cases ultimately succeeded by a short-lived and easily missed 
resumption on the part of the split chromatic thread-work of its earlier 
polarised arrangement; and this is followed by a strong Second Con- 
traction and thickening of the individual loops.” 
It is very certain that in none of the Orthoptera which I have studied 
are there two contraction figures such as Farmer and Moore describe, 
nor is there at any time a continuous spireme. As I have previously 
described in detail, the original polarity persists until immediately 
previous to the time when the definitive tetrads are formed, and is 
then lost by the loops becoming detached from the nuclear membrane. 
In all cases the loops can still be seen to retain their connection with 
the pole even after they have opened out and assumed a peripheral 
position, while in some species the polarity is easily distinguished up 
to the time when the loops become free. Possibly the results of 
Farmer and Moore may be explained on the supposition that in 
Periplaneta, where the two contraction figures are especially well 
shown, the loops retain their connection with the nuclear wall until a 
later period than in most Orthoptera. If this connection should be 
retained until the loops begin to condense to form the tetrads, it 
would result in precisely such structures as are figured by these 
authors, except that between the two contraction figures the loss of 
polarity is only apparent. 
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