DR. MARTIN BARRY’S RESEARCHES IN EMBRYOLOGY. 
533 
and even into a certain part of the altered germinal spot. We have seen this part 
tending towards the surface of the ovum. I have now to add, that in that region of the 
thick transparent membrane f, towards which this part was tending, I have in many 
instances observed an attenuation or an orifice. This has been noticed not only as 
early as the fourth hour (fig. 165.), but in very mature ova'f-, even ante coitum. The 
form of the orifice in question is sometimes such as to suggest the idea of the mem- 
brane having become cleft ; in some instances appearing to have been first attenuated 
also. 
333. Should this observation be confirmed, I think we shall be in possession of 
very strong presumptive evidence that the central part of the altered germinal spot is 
the point of fecundation. In further proof that such really is the case, another fact 
will be hereafter given (par. 346.). 
334. On one occasion, in an ovum of 5^ hours (fig. 167-)? I saw the orifice of the 
membrane/*, an object very much resembling a Spermatozoon which had increased in 
size. Its large extremity was directed towards the interior of the ovum. Fig. 168. 
represents a portion of this object ; the remainder having been too indistinctly seen 
to admit of delineation. The part figured seemed discoid in its form, and appeared 
to contain a pellucid and nearly central cavity^. 
335. Around the orifice in the membrane f (Plate XXIII. fig. 173.), the tunica gra- 
nulosa presents the effects of the determinate pressure by which the ovum had been 
held in contact with the wall of the ovarian cavity §. 
Preparatory Changes in the Substance by which the Germinal Vesicle is surrounded. 
336. This substance, usually called the “ yelk,” was described in my last paper, as 
ceasing to contain separate oil-like globules when the ovum becomes mature ; and 
as presenting a peripheral stratum which sometimes appears granular, and at others 
seems to consist of vesicles (cells), pressed together into a polyhedral form, its centre 
being fluid. The accuracy of this description, several conditions of the ovum repre- 
sented in Plate XXII. confirm ; and later observations enable me, I believe, to point 
out the order of these different appearances, as well as the process to which they are 
referable. 
337- If fig. 156. be closely examined, the substance lying under the membrane f will 
be seen to have consisted of a layer of very regularly elliptical and flattened objects, 
each of which contained minuter objects of the same kind, concentrically arranged 
around a pellucid point. These discoid objects, the containing as well as the con- 
i' From the same Rahbit as the objects in figs. 158. 159. This Rabbit exhibited marks of the most perfect 
preparation for the male. 
t I am not prepared to say that this was certainly a Spermatozoon, but it seems proper to record the obser- 
vation. 
§ See remarks on the office of the Retinacula ovi in my “ First Series.” Philosophical Transactions, 
1838, Part II., p. 86. 
