54 
Katharine Foot and E. C. Strobell 
with theoretical prejudice, we may at least call attention to the e\idence 
in Euschistus crassus for the consideration of those who regard the plane 
of division of the chromosomes as fnndamentally important. Frequently 
the e\ndence at the prophase is diametrically opposed to that of the 
metaphase and in these cases the facts observed at the prophase would 
seem to be more reliable, as the chromosomes are less Condensed and their 
structural details are more clearly defined. This is illustrated in the i 
apparent longitudinal division of the large chroniosome in the first division 
of photos 24 — 28 while in photo 22, on the contrary, the same chromo- 
some is in the form of a ring, separating transversely at two points and 
each half showing a longitudinal split presumably foreshadowing a longi- 
tudinal division in the second spindle. In spite then of the evidence 
of a longitudinal division given in photos 24 — 28 the prophases shown i 
in photos 21 and. 22 apparently justify us in concluding that the first i 
division of this chromosome is transverse. 
Even if we are satisfied that the plane of division can be definitely ' 
determined at the prophases, the interpretation of the plane can still ' 
be a matter of controversy. For example, those who would harmonize 
the method of reduction of the “ordinary chromosomes” with that of 
the idiochromosonies can assume that the longitudinal split in the ring 
of photo 22 indicates the line of an earlier parallel conjugation, and that 
therefore its second di\nsion separates “univalents”. Such an interpreta- 
tion by those who believe that one di\ision is reducing and the other 
equal involves the assumption that the first division of this chromosome 
must be equational, an assumption that is challenged by the e^ndence 
of its transverse division demonstrated in photos 21 to 23. 
If we are to give consideration to the prophase stages of the idio- 
chromosomes, the evidence points to a longitudinal division of the large 
idiochromosome and a transverse division of the small idiochromosome. 
The two idiochromosomes are shown on the right periphery of photo 22, 
the large one having a longitudinal split and the small one a transverse 
split. This is again demonstrated in the prophase of photo 23. The 
two idiochromosomes are in contact on the left periphery, the large one 
showing a longitudinal split while the cleft of the small one is at right 
angles to this and divides the small idiochromosome transversely^). As 
stated above, we realize that the form of the chromosomes, even at the 
prophase, does not offer infallible evidence as to the plane of division 
1) If the printing of the plate is a little too dark, these clefts may be obscured, 
but they are present in the negatives. 
