52 
Katharine Foot and E. C. Strobell 
a structure is constantly present, tve would maintain our former reserve 
011 this point. Of its absence in our smear preparations of EuscMstus 
variolarius, we wrote ('09): “We have not been able to demonstrate its 
presence at any stage of the growth -period of the spermatocytes. In 
sections we often find faintly staining areas that might be interpreted 
as an achromatic nucleolus, but in tdew of the possibility of artefacts 
in such preparations, we hesitate to interpret them as true nucleoli, 
unless we can support the interpretation in our smear preparations. 
Until this point can be settled we are not justified in drawing any conclu- 
sions from the obvious difference in type between the nucleoli in the 
male and female cells of Euschistus." Pg. 223. 
That Moxtgojiery’s ('11) Identification of an achromatic nucleolus in 
the spermatocytes of Euschistus variolarius is due to any superiority of 
his technique we can hardly believe, for the reason that our technique 
is able to demonstrate details that he says he is unable to differentiate. 
We have a number of photographs of Euschistus variolarius (30 in all) 
in which the large idiochromosome is clearly identified at the meta- 
phase, the stage at which Montgomery States, ‘It can no longer be di- 
stinguished from the Autosomes.” Pg. 757. Further, we have had no 
difficulty in demonstrating achromatic nucleoli in the oöcytes, and we 
therefore find it impossible to accept as adequate the explanation that 
their absence in our preparations of the spermatocyte is due to defective 
technique. 
The photos of plate 11 demonstrate that no achromatic nucleolus is 
present in our preparation of the first spermatocytes of Euschistus crassus. 
The point of interest in this form is the fact that the so-called sex chromo- 
sonies are not the only chromosomes formed from a chromatic nucleolus, 
but another pair of chromosomes is also formed from a second nucleolus. 
This would seem to challenge a too serious consideration of this structural 
feature associated almost universally with the so-called sex determining 
chromosomes, and which has been one factor tending to set these chromo- 
somes apart as fundamentally unique. The fact that a second nucleolus 
gives rise to a pair of so-caUed “ordinary chromosomes” is certainly a 
striking bit of e\ädence for homologizing the chromatin nucleolus of the 
spermatocytes with “the nucleolus which in some form is said to give 
rise to all the chromosomes”. Foot and Strobell '10. 
A further point of interest in Euschistus crassus is the fact that in 
the germinal vesicle a large chromatin nucleolus is present (plate IV), 
a structure that is eonspicuously absent in other Euschistus species. It 
is demonstrated in the early leptotene stage of photo 54, but in earlier 
