64 THE AMERICAN MONTHLY _ [Apralk 
which I interpret as meaning that the basal end of the cells here are very 
irregular. Very likely many of them are continuous with fibres from the 
olfactory nerve, though this is merely conjectural. The sections show further 
an appearance in many cells, which, if my material had been perfectly pre- 
served, I should unhesitatingly interpret as due to the presence of cilia, and 
I have but little doubt that the cells at the tips of the papilla are many of 
them ciliated cells. 
The precise shape of the cells from the papilla and their connection with 
the fibres, if they have one, as seems probable, could be shown upon teased 
preparations. I had hoped to be able to investigate the matter in that way 
before this time, but have been unable to do so. 
I wish, in this connection, to make mention of a tract of very peculiar 
epithelium encountered in studying the gills of Crepidula, and further, in 
studying the osphradium, though I do not feel prepared to assert that it is 
sensory in function. It is situated upon the branchial ridge upon the part 
turned toward the groove which lodges the osphradium, and is composed of 
tall granular cells. These, in cross-sections, look like a sort of cup or pocket, 
but longitudinally they are seen to be a long row or ridge which runs along 
the back of the gill-ridge throughout its entire extent. They are entirely 
unlike any cells seen anywhere else in the ectoderm, and are possibly glandu- 
lar in their function. 
Purpvug University, ec. 21, 1886. 
A key to the Rotifera.* 
By Dro ias: SLE VENs; 
OF TRENTON, NEW JERSEY. 
The following key is intended to facilitate the use of Hudson and Gosse’s 
monograph on ne Rotifera, and includes only the genera and species de- 
scribed in that work. In the analytical table of genera, the numbers appended 
to each name direct to that genus in this list, where a synopsis of the species 
will be found. 
GENERA. 
| Permanently adherent, not in social colonies, but sometimes in family 
groups ($). 
{| Permanently adherent in social clusters ($$). 
| Free-swimming in clusters ; tubes cohering, gelatinous, Cozochzlus, 12. 
{| Free-swimming, solitary ($$$). 
§ Corona subcircular or broadly oval (*). 
§ Corona cup-like or produced into lobes (**). 
§§ Clusters fixed; tubes cohering, gelatinous, corona cordate. 
Lacinularta, 9. 
§§ Clusters fixed, without tubes; corona reniform . Megalotrocha, 10. 
§§§ Free-swimming and skipping by 6 limbs. . . . | Pedalianwey 
§§§ Free-swimming only ; cilia equator ial; body spherical, 
Trochosphera, Ul. 
Free-swimming or floating ; corona a membranous cup; foot none, 
Afpsilus, 3. 
Free-swimming, but in gelatinous tube ; lobes 2, setigerous, 
Flosculartia, \. 
Free-swimming and creeping like a leech ; toot wholly telescopic (4). 
Free-swimming and sometimes cr cHEERIe by the toes (c). 
we Tr 
Sr Gr 
wr Sr 
Lr LF 
Dr Dr 
Lr Lr 
* From the Tocca of the Trenton Natural Ee ious Society, January, 1887. 
