A Study of Chromosomes and Chromatin Nucleoli in Euschistus crassus. 57 
tified, thoiigh not always, for exaraple in the left group of photo 25 it 
is distinctly larger than the next in size, biit in photo 29 the sanie two 
bivalents are so nearly equal in size that they cannot positively be 
differentiated. Further variations in relative size can be seen in the 
somatic groups, even the two large chromosomes sometimes showing 
a marked inequality as to their chromatin content. This is most 
apparent in photos 39, 42 and 43, but such inequality is not evident in 
either the first or second metaphase. 
We have demonstrated a like inconstancy in the form of the chromo- 
somes and in a recent paper on Protenor we gave a brief summary of 
these results as foUows: “Of the presence of rings and crosses in Allo- 
lobophora foetida (1905) we stated: ‘We find no constant form differences 
of the chromosomes . . . They present a variety of shapes, rings, figures 8, 
crosses etc. without any regularity or constancy ... In some cases 
aU the eleven chromosomes are rings and sometimes not a single ring 
is found.’ In Anasa tristis (1907) we found similar irregularities — for 
example the cross form is not always associated with a definite chromo- 
some, though ‘there is a frequent repetition of certain forms’”. Foot 
and Strobell ('11). 
We may add to this evidence the demonstration of the single cross- 
shaped chromosome on the upper right periphery of the group of photo 23, 
a feature which is not constant. We may add the further evidence that 
we have a few photographs in which one or two ring-shaped chromo- 
somes are clearly demonstrated in the first metaphase of Euschistus vario- 
larius, a stage in which Moxtgomery ('11) States none are found. “Chro- 
mosomes most difficult of interpretation are ring-shaped ones, and for- 
tunately Euschistus has none such in the maturation mitoses.” 
Such structural variations are in harmony with the conception of 
those who regard the chromosomes as “an expression of the organizing 
function of the ceU as a whole”. Farmer ('07). Like other organs they 
may have characteristic features that are typical of the species or the 
genera, or the family, and variations in any of the features whether 
relative size, form or number, are added evidence that the chromosomes 
of the cell have much in common with other organs (“körperliche Eigen- 
schaft” Fick '07). 
If one is anxious to force the number of chromosomes of Euschistus 
crassus into the number typical of so many Euschistus species (14) it 
might be claimed that two male and two female chromosomes have 
fused, thus the kargest bivalent of the first spermatocyte, representing 4 
instead of 2 chromosomes, and the same chromosome in the second 
