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Katharine Foot and E. C. Strobell 30 
two spermatogonial chromosomes rather than one, then we should be 
able to add to the evidence given above for the second division of this 
chromosome, the further evidence of a demonstration of twenty-two 
chromosomes in the spermatogonia instead of twenty-one as figured by 
Wilson and Montgomery. This evidence we give in Photos. 47 to 50, 
each preparation showing twenty-two spermatogonial chromosomes. 
Our appreciation of the difficulty of demonstrating the number of 
chromosomes in the spermatogonial cells we expressed in our preliminary 
note as follows: “We realize in common with all cytologists the diffi- 
culty of getting a correct count of so large a number of small bodies 
crowded into a contracted space. If two or more chromosomes are in 
such close contact that their line of separation is obscured a correct count 
is impossible. It is certainly possible to find cells in which only twenty- 
one chromosomes can be differentiated and still easier to find cells in 
which only twenty or nineteen are defined. It is much more difficult 
to find each chromosome so distinctly isolated that all can be demon- 
strated in one photograph.” We have, in fact, many photographs of Anasa 
in which only eighteen, nineteen, twenty, and twenty-one spermatogonial 
chromosomes can be counted, but we have not thought it necessary to 
publish these for such negative evidence merely illustrates one of the 
elementary difficulties encountered by every cytologist. 
We believe the early spermatogonial prophase the most favorable 
period for an accurate counting of chromosomes, for at this stage the 
chromosomes are less closely grouped and have not yet begun to con- 
tract into the smaller denser forms they assume just before division. 
This is shown in the first spermatocyte by comparing Photos. 21 to 24, 
Plate I, with Photos. 13 and 14, Plate II, and the extent of such con- 
traction of the spermatogonial chromosomes is illustrated by comparing 
Photo. 47 with Photo. 50. The prophase shown in Photo. 47 clearly 
demonstrates twenty large chromosomes and the two microchromosomes 
one of these attached to one of the large chromosomes. The position of 
these microchromosomes is shown in a diagrammatic sketch of this photo- 
graph enlarged one diameter, reproduced in Text Fig. 4. An enlarged 
photograph was taken of the original negative and Text Fig. 4 was 
traced from a print of this enlarged negative. The individual chromo- 
somes are numerically paired in this sketch merely to emphasize the 
absence of an odd, unpaired chromosome—but we have made no pre- 
tense to accurate pairing of the many chromosomes which show only a 
slight variation in size. Twenty-two spermatogonial chromosomes are 
again demonstrated in Photos. 48, 49, and 50. Just below the upper 
