568 
DR. NELSON ON THE REPRODUCTION OF THE ASCARIS MYSTAX. 
How then is the spermatic particle formed? I have described the tendency of the 
nuclear membrane to become more and more convex ; as this convexity increases 
the apex impinges more or less obliquely against the cell-wall (figs, 28, 32, 33 a), 
protruding it slightly at the same time that it is itself diverted from the straight 
course, becoming bent into a curved form (figs. 29, 30 f). By this time the granular 
portion of the nucleus has become much diminished in volume, still presenting, 
however, the nucleolus (fig. 34 c) ; while the nuclear membrane has passed from the 
conical to a cylindrical shape (fig. 34 f). During these changes in form, the nuclear 
membrane likewise increases in thickness, and presents a double outline (figs. 29 
to 34 /'), and refracts light strongly. 
By contraction in its transverse diameter and elongation in the other, it gradually 
assumes the form of a test-tube (figs. 35, 36/”), bent, however, to adapt itself to the 
concavity of the spermatic cell (figs. 35, 36 a), often making a curve of a quarter of 
a circle. 
From the period at which a double outline is first visible, the granules begin to 
disappear (figs. 29, 30 Z>), till at last the nucleus (fig. 22 h) becomes entirely trans- 
formed into an elongated ceecal tube (figs. 35, 36 /”) with very thick sides, the cavity 
being occupied by a dark homogeneous substance, while at its mouth is found 
the nucleolus (figs. 35, 36 c) and a few granules that have not yet disappeared 
(figs. 35, 36 h ) ; the whole, however, still enclosed within the spherical spermatic cell 
(figs. 35, 36 a). 
The blind extremity next enlarges slightly, while the enveloping cell dissolves, and 
a fiask-shaped body, the true spermatic particle, is thus set free (fig. 38). 
Although the disappearance of the spermatic cell occurs normally at this period, 
it often happens much sooner, and thus we find the spermatic particles set free in all 
stages of their development, from the primitive nucleus (fig. 37 V) to the perfect con- 
dition (fig. 38). 
In many of these spermatic particles the nucleolus (figs. 37, 38c) still remains; 
but it also in course of time disappears, leaving the mouths of these hollow bodies 
apparently open (fig. 38 g). 
Originally the nucleated cells (fig. 18 a) in the cmcal extremity of the testicle 
(fig. 8) are not more than T oooo tlJ of an inch in diameter; as they descend 
they become enveloped by granules, at first forming irregular masses about j- g^^ th 
of an inch (fig. 19), but by gradual consolidation become the round, opake bodies 
which I have called granular masses (fig. 20 a), measuring jth of an inch in 
diameter, and containing each a single spermatic cell, now, however, increased to 
y^gyth of an inch (fig. 20 c). 
After the spermatic cells are introduced into the female uterus they enlarge 
rapidly, and are met with measuring from roVoth to y^th of an inch (figs. 21 
to 36). The nucleus is about one third the diameter of the cell, or about y /og th 
