554 
DR. MARTIN BARRY’S RESEARCHES IN EMBRYOLOGY. 
incipient growth in the germ of the inammiferous ovum, in the following respects ; 
namely, Schleiden does not state that the nucleus performs any part in the formation 
of new cells ; or that only two — of many cells arising — succeed the parent cell-f*. 
399. Figs. 235 to 243 Plate XXVIII, copied from delineations by Schleiden;*;, repre- 
sent the vegetable “embryo” (germ) in very early stages. On comparing them with 
certain states of the inammiferous germ, I find it difficult to believe that they do not 
result from essentially the same process §. Thus the upper part of fig. 23/. admits 
of comparison with the essential portion of the ovum in several figures of Plate 
XXIII.; the upper part of fig. 238. with bs in Plate XXVI. fig. 206 ; the upper part 
of fig. 239. with bs in Plate XXVI. fig. 212 ; the upper part of fig. 240. with bs in 
Plate XXVI. fig. 220 ; the upper part of figs. 241. 242. with Plate XXVII. figs. 233 
and 234. In the last-mentioned figures, perhaps the “ punctual vegetationis ” of 
Wolff (figs. 241. 242. 1) is represented in the mammiferous ovum (Plate XXVII. 
figs. 233. 234.) by the rudimental embryo ( bb ), and the incipient cotyledons by the 
remainder of the germ. 
400. Thus the germ of certain plants passes through states so much resembling 
those occurring in the germ of mammiferous animals, that it is not easy to consider 
them as resulting either from a different fundamental form, or from a process of de- 
velopment which, even in its details, is not the same as what has been above described; 
the fundamental form in question, in Mammalia, and therefore it maybe presumed in 
Man himself, being that which is permanent in the simplest plants, — the single iso- 
lated cell ||. 
Recapitulation. 
401. The almost universal supposition, that the Purkinjean or germinal vesicle is 
the essential portion of the ovum, has been realized in these investigations ; but in a 
manner not anticipated by any of the numerous conjectures which have been pub- 
lished. The germinal vesicle becomes filled with cells, and these again become filled 
with the foundations of other cells ; so that the vesicle is thus rendered almost opake. 
The mode in which this change takes place is the following, and it is one which, if 
confirmed by future observation, must modify the views recently advanced on the 
mode of origin, the nature, the properties, and the destination of the nucleus in the 
physiology of cells. It is known that the germinal spot presents, in some instances, 
a dark point in its centre. Such a point is invariably present at a certain period ; it 
enlarges, and is then found to contain a cavity filled with fluid, which is exceedingly 
f It is deserving of notice, however, that in reference to Marchantia polymorpha Schleiden states, “ Of the 
cell-germs [cytoblasts] found in the spores, few only — at the most two to four — serve for the formation of cells ; 
the others soon becoming covered with chlorophylle, and thus withdrawn from the vital process.” ( l . c., p. 157.) 
+ L. c., tab. iii. fig. 17. Wiegmann’s Archiv, 1837, tab. vii. figs. 13 to 15, and figs. 6. 7. 1G. 17. 8. 
§ See also a remark in my “ Second Series,” l. c., par. 318. Note. 
II See remarks in my “ Second Series,” l. c., par. 318. Note, par. 312. 
