I. ASTUDY OF CHROMOSOMES IN THE SPERMATOGENESIS 
OF ANASA TRISTIS- 
BY 
KATHARINE FOOT anp E. C. STROBELL. 
WITH 3 PLATES AND 4 TEXT FIGURES. 
Valuable contributions to our knowledge of the spermatogenesis of the 
Hemiptera have been made in recent years by Paulmier, 99; Mont- 
gomery, OI, 06; Gross, 04, and Wilson, 05-06, and Professor Wilson 
has recently created a new interest in this branch of cytology by con- 
tributing the authority of his support to McClung’s hypothesis that in 
the definite distribution of a given chromosome we may have a morpho- 
logical explanation of the determination of sex. Though Professor 
Wilson differs from McClung in some important particulars, they both 
agree as to the dimorphism of the spermatozoa, but McClung, 02, claims 
that spermatozoa (Orthoptera) possessing one extra chromosome produce 
males, while Wilson claims that spermatozoa (Hemiptera) lacking such 
an extra chromosome produce males. 
Among the investigators of the spermatogenesis of the Insecta there 
is a striking agreement as to the fact of the dimorphism of the sperma- 
tozoa, most of them maintaining that half the spermatozoa receive one 
more chromosome than the other half, though there is an equally strik- 
ing disagreement as to the time this unequal distribution of the chro- 
matin takes place. It is held that in some forms this unequal distribu- 
tion is caused by the omission of the division of one of the chromosomes 
of the first spindle and in other forms by the omission of the division of 
one of the chromosomes of the second spindle. This difference is not 
definitely associated with a given order. In the Hemiptera, for example, 
Professor Wilson finds eight forms in which the division of one of the 
chromosomes is omitted in the second spindle and two forms in which 
it is omitted in the first spindle, and Miss Stevens, 06, finds a similar 
inconsistency in Aphrophora. 
In the spermatogenesis of Anasa tristis there are notable contradic- 
‘We are indebted to the courtesy of Dr. P. R. Uhler for identifying our 
material. 
AMERICAN JOURNAL OF ANATOMY.—VOL. VII. 
