The Chromosomes of Euschistus variolarius, Eusehistus servus etc. 51 1 
Wilson, E. B. ’06. Studies on Chromosomes III. The Sexual Differences of the 
Chromosome groups in Hemiptera, with Some Considerations on the Deter- 
mination and Inheritance of Sex. Journ. Exp. Zool. Vol. III. Nr. 1. 
• T2. Studies on Chromosomes VIII. Observations on the Maturation-Phenomena 
in Certain Hemiptera and Other Forms, with Considerations on Synapsis 
and Reduction. Journ. Exp. Zool., Vol. XIII. Nr. 3. 
Explanation of Plate. 
Plate XXXVI. 
The photographs were taken by our method of focussing described by Foot and 
Strobell ’Ol, and in all cases the magnification of each photograph on the plates is 
1000 diameters (Zeiss 2 mm. apo. immer. lens, com^ oc. 4). 
The photos are from smear preparations, and in the chromosome groups of each 
photograph every chromosome of the group is demonstrated. The reproductions are 
bromide prints. 
Photos 1 — 9. E. variolarius. 
Photos 1 and 2. Late prophase chromosomes of the first spermatoc 3 'te mitosis. 
In photo 1 the X Y chromosomes appear well separated on the right periphery of the 
group. In photo 2 they appear as a tetrad on the left periphery of the group. 
Photos 3 and 4. Sletaphase chromosomes of the first spermatocyte mitosis. 
In photo 3 the X Y chromosomes are below the bivalents and are dividing as univalents, 
and in photo 4 also each is di\nding as a univalent, while the autosomes are dividing 
as bivalents. 
Photos 5 — 8. Metaphase chromosomes of the second spermatocyte mitosis. In 
each of the 4 groups the X Y chromosomes are clearly distinguished on account of their 
inequahty in size. On the left periphery of photo 6 are shown two of the autosomes 
apparently constricting off a small particle of their chromatin, as described on p. 492. 
Photo 9. Telophase of the second spermatocyte mitosis. The chromosome 
groups of the two spermatids show the X chromosome in the center of the left group 
and the Y chromosome in the center of the right group. 
Photos 10 — 15. E. servus. 
Photos 10 — 12. Metaphase chromosomes of the first spermatocyte mitosis. In 
each of the 3 groups the X Y chromosomes are nearly in contact and are clearly dist- 
inguished from the autosomes. Each is dividing as a univalent while the autosomes 
are dividing as bivalents. 
Photos 13 — 15. Metaphase chromosomes of the second spermatocyte mitosis. 
The X Y chromosomes are nearly in the center of each group and are easily identified 
on account of their inequality in size, which is fully as marked as the inequality in size 
of the XY chromosomes of variolarius. (Compare photos 10 — 15 with photos 1 — 9.) 
We have selected these photographs of servus from material that was collected in both 
Texas and N^orth Carolina. Photos 10, 14 and 15 are from North Carolina specimens 
and photos 11^ — 13 from Texas material. 
