680 REVIEWS AND BOOK NOTICES. 
Tue ORIGINAL DISTINCTION oF THE TESTICLE AND Ovary.* — 
An interesting contribution to the germ layer or Gastrea theory 
of Haeckel, which is now exciting the attention of embryologists 
and evolutionists, is afforded by Prof. E. Van Beneden of Liége. 
It will cause an inquiry into the real value of Haeckel’s Gastræa 
theory, disputed by some of our leading zoologists. We translate 
Van Beneden’s introduction and conclusions. 
of the Coelenterata, and the two primordial cellular layers of verte- 
brates. See in what terms he expresses this idea; ‘the pecui- 
arity in the structure of the body-walls of the Hydrozoa, to which I 
have just referred, possesses a singular interest in its bearings 
upon the truth that there is a certain similarity between the adult 
states of the lower animals and the embryonic conditions of 
higher organizations. 
‘For it is well known that, in a very early state, the germ, ee 
drozoon and the embryonic vertebrate animal.’ All the embryo 
logical researches made in 
ara sexuel des denx 
e de toute mdi- 
y 1874. 89% 
* De la Thioti 
Feuillets primordiaux de PEmbryón; Hermaphrodisme morphologiqu 
vidualité anim Essai d’une Théorie de la Fécondation. Bruxelles 
t tion of at 
tions upon the Anatomy of the Diphydz and the br of Organizi 
4 i Roya 
t Observati 
the Diphydæ and Siphonophoræ. Proceedings Royal Society, 184 
