Huxley on Lacinularia socialis. 
3 
a lower (p'), of which the former is the thicker and extends 
beyond the latter. 
The large cilia are entirely confined to the upper margin, 
and, seated upon it, they form a continuous horseshoe-ahaped 
band, which, upon the oral side, passes entirely above the 
mouth (fig. 4). The lower margin {p') is smaller and less 
defined than the upper, its cilia are fine and small, not more 
than l-4th the size of those of the upper margin. On the oral 
side this lower band of cilia forms a V-shaped loop (fig. 4), 
which constitutes the lower and lateral margins of the oral 
aperture. About the middle of this margin, on each side, 
there is a small prominence, from which a lateral ciliated 
arch runs upwards into the buccal cavity, and, below, becomes 
lost in the cilia of the pharynx. 
The aperture of the mouth therefore lies between the 
upper and lower ciliary bands. It is vertically elongated, 
and leads into a buccal cavity with two lateral pouches, which 
give it an obcordate form ; these lateral pouches contain the 
lateral ciliated arches. A narrow pharynx leads horizontally 
backwards from the lower part of the buccal cavity, and 
becomes suddenly widened to enclose the pharyngeal bulb in 
which the teeth are set. Where buccal cavity meets the 
pharynx, a sharp line of demarcation exists (fig. 2). In Meli- 
certa two curved lines are seen in a corresponding position, and 
evidently indicate two folds (PI. II. fig. 26), projecting upwards 
into the oesophagus. In Brachionus these folds are stronger 
(fig. 31), while in Stephanoceros and Floscularia this partition 
between the oesophagus and what may be called the crop is 
still more marked. From the inner margin of the aperture 
in the partition two delicate membranes hang down into the 
cavity of the crop, which have a wavy motion, and it is to them 
I think that what Mr. Gosse describes as an appearance of 
" water constantly percolating into the alimentary canal " is 
due. Dujardin had already noticed (1. c, p. 98) these 
"vibrating membranes" in Floscularia (' Infusoires,' p. 611). 
Between the pharyngeal bulb and the mouth there lies on 
each side of the pharynx a clear, yellowish, horny-looking 
mass (jf), which sometimes appears merely cordate, at others 
more or less completely composed of two lobes. A similar 
structure exists in Brachionus and Melicerta. I believe its 
function is to give strength to the delicate walls of the 
pharynx, and that it is therefore to be considered as a part of 
the horny skeleton.* 
* Leydig (loc. cit.) calls these bodies sacs, and considers them to be 
salivarv glands. 
b 2 
