SEXUAL CHARACTERISTICS OF THELIA 593 
females (9.78 mm.) than the average length in normal males 
(8.13 mm.). The pattern of the face also showed a decided loss 
of male characteristics and an assumption of those of the female. 
Turning now to the abdomen (fig. 49), we find there also strik- 
ing changes. The terga form a sharp ventrolateral angle where 
they join the pleura and the cuticula shows a marked reduction 
of melanic pigment and has become more pliable. Examined 
microscopically, the terga exhibited the arrangement of the 
minute spines in the pattern characteristic of the female (figs. 
32 to 35). The tergum and pleura of the ninth abdominal seg- 
ments fused together and became longer than those of normal 
males. The oedagus and claspers were greatly reduced in size. 
The most interesting feature about the male Thelia described 
above is that in the right half of the abdomen there was located 
an entire testis, normal in size. This was immediately removed 
and placed in Bouin’s fluid, drawn with the aid of a camera 
lucida to obtain its exact dimensions, and then imbedded and 
sectioned. All stages of active spermatogenesis were found. 
There were spermatogonia quiescent and in mitosis, spermato- 
cytes in growth and maturation, spermatids undergoing trans- 
formation, and mature spermatozoa in great numbers. Figure 
50 is a photograph of four of the tubules, and, even at the com- 
paratively low magnification used, one may distinguish the 
cysts of spermatozoa with their deeply staining heads lying side 
by side. The mitoses found in this testis were in every way 
normal and the large, lagging, unpaired x-chromosome is as 
noticeable as in any normal first spermatocyte division (fig. 51, 
e and f). 
The testis above described was the largest ever found in a 
parasitized Thelia which showed marked somatic changes. 
Other testes have been taken from altered males, but these in- 
variably showed many abnormal mitoses, many stages of fatty 
degeneration, and broken-down cysts devoid of spermatozoa. 
These have been sectioned and studied and will be reported upon 
at a future date. The important fact to be noted about this 
male is that, in spite of the presence of a normal testis, the para- 
sites exerted a marked influence on the developing soma. This 
