254 
Sidney I. Kornhauscr 
It has been inipossible to establish the identity of the X-chromosome 
by its beliavior at auy stage in the spermatogonial generations. Kot 
luitil the chromosouies of the telophase of the last spermatogonial divi- 
sion had becoine indistinct, did a well marked deeply staining nucleolus 
appcar, 
The oögonial nuinber of chromosomes in E. curvata is twenty 
(Plate XIX, Figs. 37, 38), one inore clu’omosome being present in the 
female diploid group than in the male diploid group. The macrochromo- 
somes and the second pair in size can here be rccognized, and the 
remaining clu-omosonies agree weU -svith those of the male. It is im- 
possible to recognize in the oögonia which is the pair of X-clmomo- 
somes. A study of the first spermatocytes shows that the X-chromosome 
is one of the smaller round chromosomes, not differing greatly in size 
froni the components of the eight smaller bivalent chromosomes. This 
makes it impossible to distinguish vith certainty the X-chromosome in 
the sperniatogonia, or the pah' of X-chromosomes in the oögonia, from 
the other sixteen smaU chromosomes. Reasoning from work on other 
hemiptera, — Protenor (Moxtgomery, ’Ol, ’06; Morrill, ’IO) and Anasa 
(Montgomery, ’06; Wilsox, ’06; Morrill, ’IO), where the X-chromo- 
some is characterized by its size from all the other chi'omosomes, and 
is represented in the female by two X-chroniosonies, — we are safe in 
assuming that the difference in the number of chromosomes between the 
male (19) and female (20) of E. curvata is due to the presence of 2 X- 
chromosomes in the female soma. 
In Thelia Mmaculata, a membracid, the X-chromosome is the largest 
of the 21 chromosomes in the sperniatogonia (Plate XXI, Fig. 191). 
In the female diploid group (Plate XXI, Fig. 192) there are two large 
chromosomes and the \Yhole number is 22. The size of the X-element in 
this species is ^Yell brought out in the groYYth period and mitotic stages 
of the first spermatocyte (Plate XXI, Figs. 193—198). This is merely 
additional proof of the kind offered by Anasa and Protenor, and extends 
the facts to the family Membracidae, of which Enchenopa curvata and 
Enchenopa linotata are members. 
C. Comparison of the Diploid Groups of Enchenopa binotata and 
Enchenopa curvata. 
In E. bmotata the chromosomal numbers are 20 in the male and 20 
in the female: in E. curvata 19 in the male and 20 in the female. A com- 
parison of the spermatogonial and oögonial groups of E. binotata and 
E. curvata shows a great similarity, not only in the relative size of the 
