ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
617 
are still a number of unsettled questions, but on some points there is 
more certainty. It may be confidently asserted that the strongly ribbed 
type of jaw (odontognath) intergrades by imperceptible stages with the 
entirely smooth, Zonites-like type (oxygnath). “ Odontognathy ” and 
“ oxygnathy ” are therefore “ controvertible terms,” as far as classifica- 
tion is concerned, and consequently cannot be used for the separation of 
genera or even sub-genera. 
The primary groups recognized by the author are : — 
I. Eggs or young very large at birth. (1) Macroon. 
II. Eggs or young smaller or minute at birth. 
a. Female system with dart-sac and mucous gland. 
(2) Belogona. 
aa. Female system without accessories ; male with flagellum 
and appendix on penis ; no epiphallus. 
(3) Teleophalla. 
aaa. Female ditto, male with epiphallus, but no appendix. 
(4) Epiphallophora. 
aaaa. Genital system lacking all accessory organs. 
b. Jaw soldered into one piece. (5) Haplogona. 
bb. Jaw composed of 16-24 separate plates. 
(6) POLYPLACOGNATHA. 
Mr. Pilsbry defines his groups and gives short notices of the consti- 
tuent genera of each. 
Integument of Zonites cellarius.* — M. E. Andre notes certain pecu- 
liarities in the integument of this Mollusc, which have not yet been 
described. These peculiarities, which obtain in no other Pulmonate 
Gastropod, consist of crypt-like organs solely formed on the right side of 
the body, where they extend from the genital orifice to the mouth, and 
from the upper boundary of the foot to the middle of the dorsal surface 
of the body. These crypts are formed by invaginations of the external 
epithelium, and are 1/4 to 1/3 mm. deep. They vary in form, being 
sometimes simple, sometimes more or less branched, and are sometimes 
provided with swellings. The epithelium of these organs differs from 
that of the surface in that the cells and their nuclei are more elongated ; 
they have no vibratile cilia. The dorsal surface of the body is peculiar 
in the presence of very large mucous cells, so closely packed as to 
form an almost uninterrupted layer. It is not at present possible to 
suggest what is the function of the crypts. 
Development of Umbrella mediterranea.f — Dr. R. Heymons makes 
an important contribution to our scanty knowledge of the development of 
Opisthobranchs. The formation of three generations of micromeres, 
their further multiplication to the 24-cell stage, the subsequent division 
of a macromere, and the associated origin of the mesoderm are facts in 
the development of Umbrella, which are in essential harmony with what 
is known to occur in Planorbis, Neritina , and Crepidula, but they have 
not been previously observed for Opisthobranchs. After a careful 
comparative study, the author goes on to discuss the excretory organ. 
His most important result is a demonstration of the entirely ectodermic 
* Zool. Anzeig., xvi. (1893) pp. 39 and 40 (1 fig.), 
f Zeitschr. f. wiss. Zool., lvi. (1893) pp. 245-98 (3 pis.). 
