GASTEROPOUES. 283 



receptacle for the tentacular or sensitive portion, which resembles a fir 

 cone. Five or six pair, or more, of palmate branchige rise from the mar- 

 gin of the back, b, the number and dimensions depending on the age and 

 size of the specimen. Towards the posterior extremity, these gradually 

 shorten and simplify in structure, and at length degenerate into mere 

 prominences. Several organic prolongations, besides, of different charac- 

 ter, likewise issue from the anterior part. The orifice of the oviduct 

 opens under the right of the branchia of the first pair. 



The whole upper surface of the animal presents a tuberculated as- 

 pect, which is certainly heightened by the variegation and interspersion 

 of colours, sometimes exhibiting delusive appearances. 



Plain or mottled brown predominates in the colour of the Stag-horn 

 Doris ; sometimes with white extremities. Small sized live specimens, 

 of dingy white, have occurred. One, perfectly white, an inch and a half 

 long, but scarcely surviving, seemed of the same species. In such light- 

 coloured specimens, especially if young, ocular specks may be occasionally 

 recognized behind the roots of the cornicula. Besides more obscure ex- 

 amples, a white patch with a black speck appeared at the exterior basis 

 of each corniculum, in a small specimen. But observations on this sub- 

 ject have not been satisfactory. The pulsation of the heart, in favour- 

 able specimens, is very distinct, the great dilatation being backwards, as 

 a circular segment, below the first pair of branchiae. On favourable oc- 

 casions, also, two marginal channels, running along the back, may be dis- 

 covered, penetrating the roots of the branchiae, from whence they are 

 distributed towards the extremities. 



The union of these animals has been witnessed in October. It was 

 once followed in two days by spawn. On the same day, another union 

 ensued, both animals being much reduced in size, as is always concomi- 

 tant on breeding. 



The spawn consisted of two portions, each a waving rope in a loga- 

 rithmic curve. The larger, composed of three coils or volutions, was the 

 sixth of an inch in diameter, the ova pure white. Plate XL. figs. 8, 9, 

 enlarged. 



The young having come to maturity in twelve days, escaped in the 



