590 
DR. MARTIN BARRY’S RESEARCHES IN EMBRYOLOGY. 
Additional Observations. 
Received June 17, — Ptead June 18, 1840. 
431. Should the facts made known in the foregoing memoir regarding the essential 
portion of the mammiferous ovum be confirmed, it will of course be inferred that the 
same changes take place, and for the same purpose, in other ova. Having however 
been so fortunate as to discover that such really is the case, I think it proper to 
record my further observations ; more especially as some of them happen to have 
been made on ova which, when compared with the ovum of Mammalia, seem at first 
sight to present an important difference. 
432. The principal observations hitherto published on the contents of the unfecun- 
dated germinal vesicle throughout the animal kingdom, were made by Professor 
Rudolph Wagner^, to whom we are indebted for the discovery of the germinal spot. 
I am truly glad that it has fallen to my lot, as I venture to believe, to show the im- 
portance of this discovery, which has been questioned. 
433. In the ovum of some animals the spot is single, — in that of others there 
are many spots ; this being the apparent difference above referred to (par. 431.). 
R. Wagner observed that the ova of certain animals in which originally there is only 
one spot, at a later period present a number ; and he conjectured that this might be 
referable to a division of the primary spot into several parts]:. It will be seen from 
what takes place in the mammiferous ovum, that this conjecture was very near the 
truth ; and facts about to be made known, will serve to explain another observation 
of the same physiologist, namely, that the number of spots in some instances increases 
as the ovum ripens. 
434. “ In Birds,” says Wagner, “ the germinal vesicle has always a germ-nucleus 
[germinal spot], which often forms a tolerably compact mass of finer molecules, but 
frequently consists of a very transparent and delicate tissue, and may thus be easily 
overlooked In scaled Amphibia the germinal spot is “at first single, but dissolves 
into several scattered points or globules, which adhere to the inner surface of the 
germinal vesicle ||.” In naked Amphibia, “instead of a single germ-nucleus or spot, 
there are always — even in the very youngest ova — several shining globules having a 
high refracting power. In maturer ova these become more numerous, but they are 
relatively and absolutely smaller, and often pressed together, being everywhere 
situated — in general but slightly adherent — on the inner surface of the germinal 
vesicle^).” The same author found the contents of the germinal vesicle in cartilagi- 
j- See the great work of Wagner, “ Prodromus Historic Generationis,” before referred to in this memoir. 
; Lehrbuch der Physiologie, I., pp. 57, 58. § A. Encykl. d. W. u. K. Erste Section xxxii. “ Ei,” p. 3. 
|| Ibid. p. 3. ^ “ Ei,” p. 3. 
