574 
DR. NELSON ON THE REPRODUCTION OF THE ASCARIS MYSTAX. 
which makes them easily distinguishable. But while the germinal vesicle enlarges 
so slightly, the ovule increases rapidly as it descends the ovarian tube, passing from 
ro^oo ^h to 2 ^th of an inch in diameter. This increase is not only owing to the gra- 
nules which appear to be accumulated from the walls of the ovary, but also to an in- 
crease in the amount of the clear substance. 
Some have supposed the increase in the number of the granules to be owing to their 
spontaneous division, while others have thought that they are formed by the germinal 
vesicle. To the first theory it may be objected, that the granules remain very much 
of the same size throughout, while those contained in the same ovule correspond 
exactly, which would not be the case if each granule were dividing into two or more. 
That the granules are not produced by the germinal vesicle is evident from its re- 
maining very much of the same size and perfectly entire. 
On the other hand, the reasons for supposing them to be formed from the walls of 
the ovary are, that the granules become more and more numerous as the ovule 
passes down the tube. Secondly, that the granules (Plate XXVIII. figs. 48, 5 1 c) 
exactly resemble in size, colour and form, those produced by the internal surface of 
the ovary (Plate XXVII. fig. 41 k). Lastly, because the strise (fig. 41 1) of the ovary 
cease just where the ovule ceases to become larger (fig. 42 A). 
The fact that the ovula were packed edgewise in this part of the tube (Plate XXVIII. 
fig. 49 c) was pointed out to me by Dr. Allen Thomson ; also that three or four occu- 
pied the same plane (fig. 50 c?). Hence the necessity of the ovula assuming the tri- 
angular form (Plate XXVII. fig. 47); the only form met with as long as the ovula 
present the appearance of a dense opake mass (Plate XXVIII. fig. 49). 
The ovary is about xioth of an inch broad at its widest part ; and here it is that we 
find the ovula packed generally four on a plane (fig. 50 d), with their edges present- 
ing externally (fig. 49 d), appearing long and narrow when viewed in profile (fig. 49 c), 
but broad and triangular when seen in front (fig. 49 b), entirely filling the transverse 
section of the tube (fig. 50 w). 
As the granules increase in number so the clear substance becomes more and more 
obscured, till at length the whole ovule appears to be composed entirely of vitelline 
granules. The germinal vesicle (fig. 48 b) can no longer be distinguished, the ovule 
being perfectly opake (fig. 50 d). In this state they are met with near the entrance 
of the oviduct (fig. 50 d ) ; they now become separated, detached singly from the mass, 
lose their triangular form (fig. 51), and by passing through the first constriction 
(Plate XXX. fig. 90 c) enter the glandular portion of the reproductive apparatus 
(Plate XXVII. fig. 42 n ; Plate XXX. fig. 90 c, d). 
When impregnation has taken place, the ovule first meets with the spermatic 
particles (Plate XXVII. fig. 42 p) in this part of the oviduct (fig. 42 n), but I think 
it may be best to trace the further changes it undergoes in the unimpregnated 
state, as they enable us to explain, or what is of more consequence, to contrast the 
appearances presented by the fecundated ovum with those of the non-vivified egg. 
