QUARTERLY CHRONICLE OF MICROSCOPICAL SCIENCE, 81 
this is of the highest interest and significance, and may serve 
to explain contradictory statements in other authors’ results), 
in the female sporosacs of Hydractinia there is an invagina- 
tion of a rudimentary character which represents the male 
organ; in the male sporosacs, on the other hand, rudi- 
mentary ovules develope in the endoderm. ‘The sporosacs 
are, therefore, primitively hermaphrodite. 
Professor Van Beneden gives very beautiful figures of the 
development of the parts in question, and his facts admit of 
no doubt. The discovery of the ectodermal origin of the 
testis and of the endodermal origin of the ovary, is one of 
jirst-rate importance. The necessary additional basis of 
observed fact, in other Coelenterata, in Vermes, &c., will, no 
doubt, soon be forthcoming, and we shall then be in a posi- 
tion to judge definitely of the value of the very important 
generalisation to which Professor Van Beneden, with much 
reason, commits himself, namely, that throughout the animal 
kingdom the testis is ectodermal, the ovary endodermal; that 
therefore the outer layer or epiblast of the embryo may be 
called neuro-muscular and male, whilst the inner layer or hypo- 
blast is alimentary, vegetative, and female. It is remarkable 
that recorded observations coincide with this. Huxley traced 
the male reproductive elements in medusz to the ectoderm, 
whilst Haeckel no less definitely assigned the ova to the 
endoderm. Allman, in writing in this Journal of the origin 
of the sexual products in Hydrozoa generally, observed that 
they appeared in a cellular mass between ectoderm and 
endoderm, which at the present could not be assigned with 
more reason to the one than to the other. But the most 
important confirmation of Professor Van Beneden’s view is 
furnished by the Vertebrata. Here, as nowhere else, the 
origin of the sexual glands has been investigated from the 
earliest stages by many observers, and by the most refined 
methods of section-cutting, &e. Van Beneden remarks that 
“it results from all the more recent embryological investiga- 
tions of vertebrata that the middle layer of Von Baer and of 
Remak gives rise only to the epithelium of the primitive 
peritoneal cavity. Now, according to the observations of 
Waldeyer, the superficial epithelium of the ovary of Verte- 
brates is only that part of the peritoneal epithelium which 
covers the middle plate (mittelplatte of Remak, intermediate 
cell-mass of Balfour and Foster). ‘lhe observations of Gétte, 
of Peremeschko, of Schenk, of Oellacher, of Rieneck, have 
demonstrated that the internal layer and the middle layer of 
Remak are but differentiated parts of one and the same 
cellular layer (the endoderm), which arises entirely from the 
_ VOL, XV.—NEW SER. rs 
