530 
DR. MARTIN BARRY’S RESEARCHES IN EMBRYOLOGY. 
has been devoted to the former, and Plate XXIII. to the latter object. In the upper 
row of figures of Plate XXIV. I have copied the only delineations published by others 
of ova from the Fallopian tube. The amount of information obtainable from these, 
will be seen on comparing with them eleven states of ova from the Fallopian tube, 
figured in my “ Second Series -fV’ and upwards of thirty more in the present paper 
323. It was stated in my last memoir § that the Purkinjean, or germinal vesicle, 
does not disappear at the period previously supposed ; but that after fecundation it 
returns from the surface to the centre of the ovum. My later researches have not 
only established the fact now mentioned, but they also enable me, I believe from ac- 
tual observation, to make known the destiny of this important object. These inves- 
tigations realise the almost universal supposition that the germinal vesicle is the es- 
sential element of the ovum ; but how far they realise any of the speculations of phy- 
siologists as to what becomes of it, will be seen on comparing the facts about to be 
recorded, with opinions quoted in the Appendix to this memoir. 
The Doctrine of “ Cells." 
324. I formerly mentioned || that Schwann ^[, basing his researches in the animal, 
upon the discoveries of Schleiden ' f-'f- in the vegetable kingdom, had demonstrated 
that in development the same phenomena are exhibited in both ; that he had shown 
animal tissues in general, like those of plants, to be reducible to modifications of vesi- 
cles or “ cells and that the mode of origin of the cells is essentially the same in 
animals as Schleiden had discovered it to be in plants. Schleiden had found, 
that the membrane of each cell is formed at the surface of the object previously 
known as the nucleus of the cell ; and in the nucleus he discovered a nucleolus. 
As the nucleolus, the nucleus, and the cell, are objects which must in future be consi- 
dered of the first importance in the structure of organized beings ; as they are con- 
stantly referred to in the following memoir ; and as my observations on two of these 
objects do not, in all respects, accord with the experience of others, it is essential to 
state existing views regarding them. These will be found in the Appendix (par. 425.). 
CHANGES IN THE OVARIAN OVUM PREPARATORY TO FECUNDATION. 
(These are represented in Plate XXII. The ova there seen measured in diameter 
from Yt'" to fi'"-) 
t L. c., Plate VI. * Plates XXIV., XXV., XXVI., XXVIT. 
§ “Second Series,” l. c., par. 133. || “Second Series,” l. c., par. 358. 
Mikroskopische Untersuch ungen iiber die Uebereinstimmungen in der Struktur und dern Wachsthum der 
Thiere und Pflanzen, 1839. 
ft Beitrage zur Phytogenesis, Muller’s Archiv, 1838. Heft II. p. 137. 
