596 SIDNEY I. KORNHAUSER 
the three pairs of appendages which form the adult external 
genitalia may be seen on the ventral side of the eighth and ninth 
abdominal segments of female fourth instars. These append- 
ages and the pigmented area of the eighth abdominal sternum 
comprise the external sexual characteristics of the nymph. 
When compared by means of camera-lucida drawings with nor- 
mal female individuals similarly mounted, the external genitalia 
and pigmented area of the eighth sternum of this anomalous 
nymph (fig. 52) were not in any way abnormal. This is a dis- 
tinct proof that in Thelia the testes do not pour forth a secretion 
which influences the developing soma, or, in other words, the 
soma is independent of the gonads in its development. And we 
may also conclude from this individual that the development of 
the gonad is to a large extent independent of the sex of the body 
in which it is found. 
An inquiry into the cause of the development of testes in this 
peculiar nymph with female soma was next undertaken. A 
cytological study of the testis proved most instructive. Sper- 
matogonia in mitosis were very abundant and handsomely pre- 
served so that the chromosomes stood out with diagrammatic 
clearness. Eight of the most favorably situated metaphase 
plates are shown in figure 54. These represented about one- 
fourth of the number of sepermatogonia in which the chromo- 
somes could be accurately counted. The drawings were all 
made with a camera lucida, and in no cases are they reconstruc- 
tions from two or more sections. Neither are the chromosomes 
shifted from their original positions. As is easily seen in figure 
54, these cells are true spermatogonia containing twenty-one 
chromosomes, the largest being the unpaired x-chromosome. 
For comparison, the chromosomes of soma and germ-plasm of 
Figs. 52 to 54 Abdomen, testis, and spermatogonia from anomalous fourth 
instar with female soma and male gonads. Figure 52, vental view of caudal 
portion of abdomen, showing external genitalia and pigmentation of eighth 
abdominal sternum; compare with figure 45. X 30.6 Figure 53, longitudinal 
section of one of the testes, showing eight tubules, each divided into cysts. X 
140. Figure 54, eight spermatogonia from testis, a section of which is shown in 
figure 53. Each spermatagonia contains 21 chromosomes, the largest being the 
unpaired x-chromosome (#); compare with figure 51, a. X 2200. 
