274 GASTEROPODES. 



conditions that their size may be conjectured. A fine specimen, extend- 

 ing six inches in health, afterwards contracted a third, and died. When 

 transferred to spirit of wine, it shrunk in a solid mass, like a double 

 wedge, two inches and a half long by an inch thick in the middle, 

 declining towards the extremities. The tentacula had disappeared, and 

 the branchige had become a regular narrow border, environing the body. 



Naturalists, in general, have been too sparing of their observations 

 on healthy living animals. M. Cuvier's dissections were of preserved 

 specimens, which, he says, had been, taken in the Mediterranean. 



Investigation of the nature of living animals can never be alike 

 satisfactory, as when their food is before us. But herein I have been 

 often greatly perplexed, and particularly in regard to that of the animal 

 we are now considering. No doubt this may have been much aggravated 

 by its sluggish disposition, and extreme susceptibility of cold. Many of 

 the lower orders feed only at a certain temperature of the atmosphere, 

 and may scarcely feed at all during the season of propagation. 



It does not appear that the substances whereon the Doris is found 

 always serves it as sustenance. It is very rarely that anything the natu- 

 ralist can offer is acceptable. Accident, however, sometimes unexpectedly 

 favours him. 



The Tritonia Hombergii feeds on the Alcyonum digitatum, the Lobu- 

 laria of modern authors, whereof a succinct account is given in the second 

 volume of \h& Rare and Remarkable Animals of Scotland. I had observed 

 smaller specimens, indeed, frequently lurking in the recesses of that pro- 

 duct, whether white or orange. But the real subsistence of no animal 

 proved more difficult to ascertain, nor wherein I had been so often dis- 

 appointed as this species. It might be partly owing to my own preju- 

 dices ; for I credited its preference of vegetable substances. 



After the preceding large specimen had been six weeks in my pos- 

 session, it continued very vigorous ; the sole spread broadly, and adhered 

 firmly to the vessel. It then fed on a small portion of the orange Lobu- 

 laria ; farther, it continued to feed upon both the white and the orange 

 species, as denoted by the secretions. 



Propagation. Many distinctions characterise the different modes ap- 



