. 
Geology and Natural History. 471 
type of Seveloineat that of Thecidium Bs of Terebratula, in 
which the observations of Kowalevsky fully agree with the previ- 
ous well known memoir of Lacaze-Duthiers on Thecidium, and of 
Morse on Terebratulina. It is not out of place to ate the very 
ungenerous treatment which Morse received at the s of many 
Conchologists for the heresies of his papers on the systematic 
from the embryology of Thecidium. In fact, all begged Bry- 
0zoa are only communities of Brachiopods, the valves of which are 
rinse and soldered together, the’ flat valve tories a united 
floor, while the convex valve does not cover the ventral valve, but 
leaves an opening more or less ornamented for the extension of 
the Lophophore. AG. 
9. Embryology of the Ctenophore ; by ALEXANDER Agassiz. 
4to, with five plates. From the Memoirs of the American Acad- 
emy of Arts and Sciences, vol. x, No. iii, August, 1874.—In this 
memoir we have a complete embryology of Tdyia roseola, and 
a nearly complete one of x eben rhododactyla, with observa- 
tions on other genera. The oir concludes with a discussion 
of the systematic position sak affinities of the Ctenophore, from 
which we make the following extracts 
e question of the fee boo sori position of the Ctenophore 
can now, thanks to the greater knowledge we have of their 
embryology, be ‘ceed | more intelligently. The position taken 
by Vogt who follows Quoy in removing them from the Acalephs 
altogether, and associatin em with the Mollusks on account 
of the apparent cemastony so strongly developed in some fam- 
ilies (Cestum, Bolina and Mertensia), seems not untenable. The 
nature of their relations to poh ms, Polyps and Acalephs, 
as well as the general relations of the Calenterata to Echino- 
derms, be discussed again, especially as having an impor- 
mary division of the animal kingdom, but also on the limits of 
Radiates, and the possible affinities of the Sponges and Celen- 
* Mr. B. P. Mann translated for me the explanation of the plates of the two 
Memoirs of Kowalevsky. 
