274 GASTEROPODKES. 
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 branchis 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 Jritonia Hombergii feeds on the Aleyonum digitatum, the Lobu- 
lavia of modern authors, whereof a succinct account is given in the second 
volume of the 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- 
