Experiments on the Respiration of Melampus. 283 
bubble below the surface, like Mel. equalis; but they never come above 
the surface; and though occasionally remaining for some time at the edge 
of the water, they generally keep quite immersed or towards the bottom. 
Experiment 7. 
I have this moment before my eye, a specimen of Melampus exiquus, 
fixed atthe edge of the water, opening and closing a notch or kind of 
orifice between two slight lobes of the mantle (on the right side, between 
the body and outer lip of the shell, near the lower corner of the aperture,) 
and letting occasionally a bubble of air escape. It is in fact exactly 
similar to the respiratory orifice which opens occasionally in a Limnea 
or Helix. The hole is so distinct now, there can be no mistake. There 
is a slight indentation or sinus in the outer lip of the shell corresponding 
to its place in the mantle. It is necessary to observe, that the opening 
and closing of this orifice takes place above the surface of the water; the 
animal having so placed itself along the edge, that the outer lip of the 
shell, together with the edge of the mantle are just out of the water: 
and that the appearance of the whole process (which I have observed for 
a quarter of an hour, the animal in that time frequently opening and 
closing the orifice) is that of its bemg done to admit or exclude air. 
Experiment 8. 
Two specimens of Melampus equalis were inclosed in separate bags of 
fine net, and immersed in the same glass of sea-water. They had each 
on the right side, a considerable way behind the tentacula, (in fact 
between the outer lip of the shells and the body, in the mantle) a large 
air-bubble, apparently standing at the mouth of an orifice;* which as 
the animal crawled about beneath the water, dilated and contracted 
occasionally, but not at regular intervals: sometimes the air-bubble was 
quite drawn in; at others protruded. On touching the animals, and 
forcing them to retreat within the shell, not only this air-bubble, but three 
or four times as much more, issued forth from this orifice, as well as from 
* Adanson, in speaking of Pedipes, says, “ Le manteau, &c. laisse 4 droit 
“ un petit trou rond auquel répond|’anus,” Hist. du Seneg.; Coquill., p. 14, 
Ihave frequently observed this orifice also in Pedipes afra, when taken out of 
the water, and forced to retreat within its shell; occupying the whole space 
between the great tooth or fold, and the lower angle of the aperture. 
