234 N. M. STEVENS, 
In regard to the reduction question, my results are entirely 
negative: the preparations show nothing that throws any light on the 
manner in which the number is reduced from 18 to 9, nor do they 
show any splitting of the chromosomes. 
As to the continuity of the chromosomes in this form, there 
is no doubt, unless, perchance, they should disappear when the nuclear 
membrane dissolves for the formation of the first polar spindle, as 
described by Kine (1902) for Bufo lentiginosus; but the close re- 
semblance in size and appearance of the smallest chromosomes in my 
sections to the nine small chromosomes found by Bovertr (1890) in 
the maturation divisions, leaves little doubt as to their continuity at 
this point. 
Spermatogenesis. 
General descriptions of the testes of Sagitta and of the circu- 
lation of masses of sperm cells in various stages of development in 
the posterior coelomic cavities are given by Hertwic (1880) and 
Grassi (1883); but the only account of the development of the 
spermatozoa from the detached spermatogonia is a paper by LEE 
(1887), whose results differ from mine on several important points. 
Lee describes the formation in the testes of polyplasts similar 
to those in Lumbricus, having a blastophore without a nucleus. I 
find no evidence of such formation in my preparations; and the pieces 
which are on the point of breaking off from the testis are of the 
same structure throughout, simply a mass of cells with large, some- 
what granular deeply-staining nuclei with one or more large nucleoli. 
A part of a section of such a mass of spermatogonia is shown in 
Pl. 21, Fig. 19, with two cells in division, others in a resting stage, 
and two approaching a division stage. Two types of spermatogonia 
divisions are found both in the testes and in the broken off portions; 
one in which the daughter chromosomes appear at the poles of the 
spindle as 18 rods, as seen in Fig. 19a and Fig. 20 in cross-section, 
and in longitudinal section in Figs. 21 and 22; and another type, 
where a much smaller number of loops, probably nine, are found at 
each pole as in Fig. 19b. Similar, somewhat smaller loops are shown 
in Fig. 23. These figures lead me to think that the so-called synapsis 
stage occurs in Sagitta at the close of the final spermatogonia divi- 
sion, the chromosomes uniting in pairs at the poles of the spindle. 
There is so much variation in the size of the spermatogonia that it 
is impossible to be absolutely certain that a resting stage where the 
chromosomes are not visible does not intervene between this union of 
