472 ; WESLEY R. COE AND STANLEY C. BALL 
vessels (lv) are likewise transposed from their normal lateroven- 
tral positions into the dorsal half of the body. 
Each gonad is surrounded by a massive wall of circular mus- 
cular fibers (figs. 2, 3, 6), as described by Cravens and Heath for 
N. pelagica. The individual muscle fibers appear to run spirally 
about the gonad. They are irregularly arranged in groups of 
from three to ten with nearly all their spindle-shaped nuclei (fig. 
3, n) next the inner surface of the wall. In transverse section the 
nuclei are oval in outline and occupy the enlarged inner borders 
of the muscle fibers. 
The general shape of the gonad resembles a retort with its 
neck directed ventrally and laterally. The germinal cells occupy 
only the body of the retort-shaped organ, the neck serving as a 
duct for the discharge of the spermatozoa. At about the middle 
of the neck of the retort (figs. 2, 3, 6) the muscular wall of the 
gonad is terminated sharply by a narrow constriction which 
marks the end of the gonad proper. The opening in this constric- 
tion (fig. 3, 0) leads into a spacious chamber, the wall of which 
consists of a single layer of cuboidal epithelium. This chamber 
serves 2s a seminal vesicle (fig. 3, sv), and into it the ripe sperma- 
tozoa collect previous to their discharge from the body. 
The opening of the seminal vesicle to the exterior remains 
closed except at the moment of discharge, and the ripe sperma- 
tozoa collect in compact bundles (figs. 3, 7, spz’) in the efferent 
duct. The hundreds of spermatozoa of a bundle all lie parallel, 
with their heads directed toward the opening. ‘The genital pore 
is guarded by a pair of lips (fig. 2) on the summit of the small 
papilla already mentioned. 
In the body of the gonad there is a small central lumen filled 
to a great extent with ripe spermatozoa (fig. 3, spz), with great 
masses of germinal cells in the various phases of spermatogenesis 
peripherally. As in most similar cases, the nuclei of these cells 
are conspicuous, but the cell boundaries are indistinct. 
Just internal to the massive circular musculature occur the 
scattered oval nuclei of the spermatogonia (spg) while the nuclei 
of the spermatocytes are arranged in groups. Those of the pri- 
mary spermatocytes are large and spherical (spe), while those of the 
