On the so-called Biogen Liquid. 401 
new being, or an element indispensable to its formation. Now 
here, among the Nemertes we meet with a case where the yolk 
is already divided into four parts, while the germinative vesicle 
still exists. 'The division of the yolk, then, can take place with- 
out the previous bursting of the germihative vesicle. 
his fact is set forth and illustrated fully in the Lectures on 
Comprehensive Embryology,* and what appears strange to us, is, 
that Mr. D. now takes for his own, an observation to which he 
strongly objected when it was first communicated to him. Hav- 
ing made his observations upon a species different from that in 
which the fact was originally*observed, there was, it seems to me, 
flicient merit in pointing it out in another species, without 
claiming for himself the absolute priority. 
If. In 1840, Mr. Martin Barry and Prof. Valentin, simultaneous- 
ly observed, the one in England in the egg of the Rabbit ; the other 
upon the shores of the Mediterranean, in the egg of a sea Urchin, 
(E'chinus lividus,) that the germinative spot is not so simple as 
had been previously supposed. 'The observations of Mr. Barry 
were published during the same year ;t those of Prof. Valentin, 
written in 1840, did not appear till 1842, and at this time he was 
Still unacquainted with those of the English micrographer, for he 
would not have failed to mention observations so curious and a 
€oincidence so remarkable. Prof. Valentin merely says that a 
round opaque body is often discerned in the center of the germi- 
native spot.{ In 1841, Van Beneden$ observed a granule in the 
germinative spot of the Hydractinia rosea, and in 1844,|| when 
reconsidering the same species, he detected an opaque corpuscle 
Within the germinative spot. This fact I have verified in 1848, 
in the case of the common sea Urchin (or sea egg) of Massachu- 
setts Bay. 
More recently Mr. D. says, that he has observed in a worm 
(Sigalion), and a sea anemone (Actinia), that the germinative 
*Spot contains a clear transparent vesicle. Comparing then this 
clear vesicle with the opaque nucleus observed by Prof. Valentin, 
é calls it Vesicula Valentini. 
We honor the homage rendered to Prof. Valentin :—but Mr. D. 
has failed to explain how it happens that a transparent vesicle in 
the worms and sea anemone, is the same thing with the opaque 
nucleus of the sea Urchins; and moreover he ought not to have 
overlooked two points of its history, those which belong to Mr. 
* Pages 70, 71. + Researches in Embryology: Third Series, 
Anatomie du genre Echinus, p. 105, Pl. viii, fig. 167. 
Bulletin de ! Académie de Bruxelles. we 
P) Recherches sur 'embryogénie des Tubulaires.—Mém. Acad. Brux., vol. xvii, p. 62, 
+ vi, fig. 6. 
Srconp Serms, Vol. IX, No. 27.—May, 1850. 51 
