Experiments on the Respiration of Melampus. 283 



bubble below the surface, like Mel. aqualis; 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 exiguus, 

 fixed at the edge of the water, opening and closing a notch or kind of 

 orifice between two shght lobes of the mantle (on the right side, between 

 the body and outer lip of the shell, near the lower corner of the apertJire,) 

 and letting occasionally a bubble of air escape. It is in fact exactly 

 similar to the respiratory orifice which opens occasionally in a Limncea 

 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 being done to admit or exclude air. 

 Experiment 8. 



Two specimens of Melampus cequalis 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 h. droit 

 " un petit trou rend auquel r^pondranus." Hist, du Seneg.; Coquill., p. 14. 

 I have 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. 



