402 ' On the so-called Biogen Liquid. 
Barry and Van Beneden. By examining more closely, and study- 
ing more intimately the contents of the germinative vesicle and 
of the germinative spot, he might have satisfied himself that the 
presence of a clear vesicle, or of an opaque nucleus, indicates only 
two states of one and the same phenomenon, since they are obe 
served alternately in the same species. This is the case with the 
eggs of Ascidie, of Meduse, of Echini, and probably the eggs of 
many others. 
merely reading the paper of Mr. Barry, he might have been 
convinced that this observer had seen much deeper than any of 
my object. I had only to point out a fact, to correct an oversight. 
1 now return to my subject. 
IV. The researches of Mr. D. upon the development of the eggs 
of Ascidie, have led him to imagine a theory. This theory rests 
upon a false fact. According to this theory, the primitive state 
of the egé isa little sphere containing a transparent homogeneous 
liquid, in the midst of which sphere, may be already seen the 
outline of the germinative vesicle and spot. By degrees this 
iquid becomes turbid, and the germinative vesicle appears sur- 
rounded by a slight cloud which increases in extent until it fills 
the sphere of the egg. Then finally there is a retreat of the mat- 
ter from the circumference towards the centre of the egg where 
it is condensed and forms the yolk. A free space remains between 
this last and the external membrane. This space is filled by a 
liquid ; this liquid is the Biogen. 
aving examined during many weeks and continuously each 
day the eggs of the same Ascidia which was the subject of his 
observation, I have never witnessed this phenomenon. And yet 
I examined them in individuals of very different sizes, and in 
most diverse conditions, taking care always that the egg should 
remain in its natural state; never, I repeat it, did I see this phe- 
nomenon of gradual condensation and of the retreat of the vitel- 
lus. Having tried all the good methods of which we can avail 
ourselves in the use of the microscope, the idea occurred to me 
to compress strongly a fragment of ovary. What was my surprise, 
at seeing living copies of the figures published upon this subject. 
It could even have been easy to make a more complete series 
of them. The eggs were no longer in their natural state; they 
were pressed down or crushed, their natural state destroyed, 
and this was the foundation upon which was built the theory 
ERS Ney ae gee ee 
