230 CEAFPOEFE: [VoL. XIV. 
and the number of chromosomes may fairly be assumed to be 
the same, eight, typical of insect ova. 
It is common among insects for the nucleus to be so small 
that it can only be distinguished with great difficulty, —so much 
so that for a long time it was said to have disappeared altogether, 
and the female pronucleus appearing later was described as a 
new structure. This has, however, been proved incorrect, and 
several writers— Wheeler ('89) in Blatta and Doryphora, Bloch- 
mann ('84), Will (85), and others — have described fully many 
complicated changes taking place in the germinal vesicle. It 
is evident from their descriptions that these changes occur 
later than do the corresponding ones in Anurida. In both 
Blatta and others the germinal vesicle remains intact until 
yolk formation has been almost completed; then the curious 
phenomena take place which render the nucleus so small; this 
is followed by the formation of the first polar body spindle, in 
which condition the egg is laid. It would seem rational to 
infer from this that the nucleus in Anurida exercises less con- 
trol over the egg during the formation of the yolk than in the 
higher Insecta; perhaps this duty is performed more com- 
pletely by the nutritive cells. No sign has been found of the 
polar body spindle nor any indication of the position of the 
nucleus until a much later stage than in other insects. In 
this respect Anurida resembles the myriapods, in many of 
which the germinal vesicle disappears early in ovarian develop- 
ment and is not seen even in the last stages. Lubbock (’61) 
says that in both Glomeris and Julus no trace of the germinal 
vesicle is ever seen in mature eggs. Zograff ('90) makes the 
same statement regarding the ripe ova of two species of Ge- 
ophilus. Schmidt (95), on the other hand, in describing the 
process in Pauropus, states that all through the period of 
yolk formation the germinal vesicle undergoes no change; it 
remains as distinct as in the younger eggs, 
Comparative and General. 
Passing from this brief description of the ovarian structure 
and odgenesis to a general consideration of the conditions of 
the ovary and a comparison with other forms, it is found that 
