A Comparative Study of the Chromosomes etc. 
273 
to the two daughter nuclei in the second division, though Boring (’07) 
described that condition for this species. 
In each spermatid one chromosome retains its stainability after the 
others have become less conspicuous (Plate XXI, Figs. 177—179). This 
is doubtless the descendant of the allosonie pair, and since both the x- 
and the ^-components stained deeply during the growth period and in 
the first maturation spindle, and since the pair divided in both mitoses, 
it is only natural to find that all the spermatids possess a deeply staining 
chromosome. It was impossible to separate the spermatids into two 
categories depending upon the degree of stainability of this chromosome; 
but from the behavior of the xy pair in the early growth period, in the 
prophase of the first spermatocyte and in the maturation divisions, two 
classes of spermatids must be formed. This is shown in a diagrammatic 
way in Plate XXII, to which I shall refer later. 
B, Enchenopa curvata. 
In E. curvata equatorial plates of the second division show nine 
or ten chromosomes with about equal frequency (Plate XXI, Figs. 180, 
181). The macrochromosome is often broad and short (Fig. 185), which 
means that the second division is longitudinal. It is therefore an equa- 
tional or homeotypic division. All the chromosomes divide and the 
a^chromosome is not distinguishable from the small autosomes. Fi- 
gures 186 and 187 (Plate XXI) show two sister anaphase plates from 
neighboring sections, the plane of section having passed through the 
equator of the spindle. 
Occasionally second spermatocyte metaphases contain nineteen chro- 
mosomes (Plate XXI, Fig. 188). This is probably due to the failm'e 
of the ceU body to divide in the first spermatocyte division. This view 
receives support from an exaniination of side views of such double second 
spermatocytes, for they often showtripolar spindles and other irregularities. 
Aside from these indications, no giant spermatocytes were encountered, 
but there were found giant spermatids and giant spermatozoa, which 
probably owed their origin to these undivided first spermatocytes. 
In E. curvata there are two classes of spermatids of equal frequency, 
those containing a deeply staining a;-chromosome (Plate XXI, Fig. 189), 
which are descendents of second spermatocytes with ten chromosomes, 
and those without a deeply staining chromosome, descendents of nine- 
chromosome second spermatocytes (Fig. 190). In Thelia himaculata the 
a>element is the largest chromosome (Plate XXI, Figs. 191—199) and 
half the spermatids have a large deeply staining chromosome (Fig. 199). 
18 * 
