DR. NELSON ON THE REPRODUCTION OF THE ASCARIS MYSTAX. 
579 
its germinal vesicle, vitelline granules, and the spermatic particles that have pene- 
trated its substance (fig. 63 h). Having entered the vitellus in different directions, 
and to various depths, the spermatic particles (figs. 61, 62 g) lose their characteristic 
form, and swell into irregular masses (figs. 61 to 63^), transparent, presenting a 
distinct outline, and highly refractive. 
These transformed spermatic particles (figs. 61 to 63 h), being situated in the midst 
of the opake granules (figs. 61 to 63 c), give the ovum a most peculiar mottled ap- 
pearance (figs. 62, 63). 
That they are spermatic particles cannot be doubted, as we meet with them in all 
stages of transformation (figs. 61, 62 g, A) ; while the regularity in shape presented 
by the large oil-globules of the false ovum (figs. 53 to 55 e) is absent, as well as the 
running together of the granules (figs. 54, 55 c) by which they are formed. 
The ovum immediately after the entrance of the spermatic particles (figs. 58 to 60 g) 
begins to acquire a chorion (figs. 61 to 63/*). The formation of this chorion does 
not appear to be dependent at all on the penetration, but to be owing to the ovum 
having reached that part of the oviduct by which the membrane is secreted, because 
we find it occurring even in the unfecundated state. 
This chorion, however (figs. 61 to 63 f), differs from the granular shell of the false 
ovum (figs. 54 to 57 f ), in being perfectly smooth, membranous and transparent 
(figs. 61 to 63 f), appearing as a single dark line, imperfect indeed at first, where 
protrusion of the granules exists (figs. 61, 62 f), but gradually encircling the whole 
ovum (fig. 63 f). 
When first formed, the chorion is flaccid (fig. 63 f), and the ovum appears of an 
irregular shape (fig. 63) ; but by the imbibition of fluid it swells up, becomes tense 
and spherical (Plate XXIX. fig. 64 f). 
The spermatic particles (Plate XXVIII. figs. 61 to 63 A), after becoming enclosed 
and swollen, begin to disappear (Plate XXIX. fig. 64 A), probably by solution, leaving 
in their place a transparent fluid (fig. 65 m). 
The vitelline granules that previous to the impregnation of the ovum formed one 
uniform, opake mass (Plate XXVIII. fig. 58 c), and partially broken up (figs. 59 to 63 c) 
by the penetration and swelling of the spermatic particles (figs. 59 to 63 A), are now 
still further excavated, separated, and detached into distinct masses by the solution of 
those particles (Plate XXIX. figs. 64, 65 c). This appears not only to be owing to the 
solution of the spermatic particles themselves, but to some direct influence that their 
solution has on the yolk, for many of the granules disappear entirely ; while others 
are changed, both as regards colour and size (fig. 66 n), a transformation totally dif- 
ferent to that which I have described as taking place in the false ovum (Plate XXVIII. 
fig. 56 c). 
Sometimes the whole vitellus is thus broken up (Plate XXIX. fig 65 c), giving the 
ovum a beautifully mottled appearance ; but more commonly it is only the surface 
MDCCCLII. 4 F 
