A Comparative Study of the Chiomosomes etc. 
249 
the edges of the ciit dose imniediately and are not “frosted” over. It 
is quite clear that E. Mnotata is a less plastic form than E. curvata, and 
certainly more spccialized. This is also shown by the restriction of E. 
binotaia to specific food plants, while curvata is a more general feeder. 
It is also an interesting fact that sonie internal parasites of E. binotata 
(larvae of certain diptera) are not found in specimens of E. curvata occurring 
in the same locality. The parasite apparently has not yet adapted itself 
to this species. The specific difference of the two species is substantiated 
in a most emphatic way by constant differences in their chi’omosomes, 
twenty being the diploid nnmber in the males of E. binotata and nineteen 
that in E. curvata. 
V. Structure of the Testes and Ovaries. 
The festes of both E. curvata and E. binotata are so much alike that a 
single description will serve for both species, and the same is true of the 
ovaries. The testes (te.) are paired, and each testis consists of eight 
conical tubules {tbl., Fig. 7, Plate XVIII) with their free or apical ends 
pointing anteriad. The tubules join at their basal ends and the mature 
spermatozoa pass through the vas deferens {va.clf.) into the large vesicula 
seniinalis (Plate XVIII, Fig. 7 vsl.sem.). A longitudinal section of the 
free end of a tubule more highly magnified (Plate XVIII, Fig. 8) shows 
the large apical cell, with its long processes, surrounded by undifferentiated 
spermatogonia and by jmung cysts. Following this, toward the basal 
end, One sees larger cysts in various stages of growth, of maturation and 
of differentiation into spermatozoa. The sequence froni younger to older 
stages corresponds fairly closely to the arrangements of these cysts from 
the apical end to the basal end of the tubule. 
The ovaries are also paired, and each consists of eight ovarioles 
(Plate XVIII, Fig. 9). Each ovariole {oal.) ends anteriad in a terminal 
Chamber (cam.trm.), which is attached to the dorsal region of the thorax 
by a long thin terminal filament (fil.trm.). In the terminal chamber 
arise ova and nutritive cells, the latter supplying a strcani of nutritive 
substance to the developing follicles in the egg string. The older eggs are 
posterior, and usually only a single one in each ovariole is fuU grow. 
The two oviducts {o'clt.) unite inta a short single uterus (ut.), which bears 
the large spermatheca {s'p'thc.) and in E. binotata the large mucUaginous 
glands (gl.muc.). For the study of the diploid groups of chromosomes, 
sections of very young ovaries in which only the terminal chamber and 
very young ova had developed were found best. Here many mitoses 
