181 
On the Structure of Amphibola avellana. 
2 . As nutrition cannot take place by means of organs of 
digestion («. e. of the entoderm) it must be effected by the 
ectoderm, by the absorption of the organic materials dissolved 
in sea-water. 
St. Petersburg, Dec. 10, 1878. 
EXPLANATION OF PLATE XX. 
Fig. 1. Bougainvillea paradoxa, Mer., normal form, enlarged. 
Fig. 2. The same, from above : a, manubrium; b, radial canal. 
Fig. 3. An abnormal individual, destitute of stomach and of buccal 
aperture. 
Fig. 4. The same, from above. 
Fig. 5. A normal Medusa of the natural size. 
Fig. 6. Another species, normal individual, rather more enlarged than 
figs. 1-4. 
Fig. 7. The same, abnormal individual, without manubrium and buccal 
orifice. 
XXI.— On the Structure of Amphibola avellana. By F. W. 
Hutton, F.G.S., Professor of Natural History in the Uni¬ 
versity of Otago, New Zealand. 
[Plate XXII.] 
MM. Quoy and GAIMARD were the first to study the 
anatomy of Amphibola avellana; and their researches were 
published in the 1 Zoology of the Voyage of the Astrolabe’ 
(vol. ii. p. 196, pi. xv. figs. 1-8). They ascertained that it 
was a true pulmonate, with the pulmonary cavity closed in 
front, and that it was hermaphrodite. So far as I know, this 
is the only description published of the anatomy of any mem¬ 
ber of the genus ; and as their account is inaccurate in several 
points, the following results of an examination I have lately 
made of the same species will not be without interest. 
The animal lives between tide-marks in salt or brackish 
water, on mud flats in sheltered bays. When found at all, it 
is always found in large quantities. It is very sluggish in its 
habits, and feeds on the vegetable matter contained in the 
mud, passing large quantities through its alimentary canal. 
Although air-breathing, it will live for a week or ten days in 
fresh water, and for more than a fortnight in salt water with¬ 
out being exposed to the air. 
I have nothing to add to the description of its general form 
given by MM. Quoy and Gaimard, except to point out that 
they overlooked the two small, flattened, triangular tentacles 
just in front of the eyes (fig. 1, c). These tentacles can be 
