218 
Katharine Foot and E. C. Strobell 
some. As to the relative sizes we have'found liere as in Anasa tristis 
enough Variation to ntake the identification of individual chromosomes 
impossible except in those cases in which the difference in size is so 
extreme that it allows for individual variations. For example in all 
the female groups of chromosomes two chromosomes are readily 
identified as larger tlian the others; bnt the relative size of these 
two large chromosomes is not constant. Photo 14, plate XV shows a 
group of fonrteen chromosomes front one of the large nuclei of zone B 
of a terminal chamber. Two chromosomes much larger than the others 
are easily identified bnt their relative size is quite different from that 
of the two largest chromosomes of some of the other groups. Photos 15 
to 18, plate XV are chromosonte groups from the smaller cells of a terminal 
chamber. In photo 15 the difference in size between the two largest 
chromosomes and the next in size is quite different from the relation 
between these chromosomes shown in photo 14. In the group of photo 16 
again the difference between the two largest chromosomes and the next 
in size is not nearly as great as in the group of photo 14 and this is also 
shown in the group of photo 17. In photo 18 however the difference 
between the two largest chromosomes and the next in size is greater than 
the relation between these chromosomes in the groups of photos 15, 16 
and 17 though not as great as in the group of photo 14. 
In the bivalent groups of the germinal vesicles (plate XX) the re- 
lative sizes of the chromosomes are also subject to variations though 
one pair larger than the others can always be identified. 
Morrill (1910) found four groups of first maturation chromosomes 
which he has demonstrated in his fig. 5 e to h. In these he shows a marked 
Variation in the relative sizes of some of the chromosomes though he 
says: “Indeed the bivalents as a whole, show the same relative size diffe- 
rences as the chromosome pairs in the oögonia.” In his figure e the 
second larger bivalent is fully twice as large as the next in size and in 
figure / the second, third and fourth large bivalents are nearly the same 
size. In the chromosome groups of our photographs 87- — 88 plate XX 
the second large chromosome is bv no means twice as large as the next 
in size, though in the oögonial group of photo 15 and 57 for example such 
a relation is shown between the chromosome pairs which represent these 
bivalents. If the size variations in the chromosomes of Morrill’s two 
groups can be set aside as due to the plane of the sections this cannot 
be offered as an explanation of a like amount of variability which is 
shown in our smear preparations. 
Exact relations are also lacking in the spermatogonial and spermato- 
