GASTEROPODES. 271 



the neck, of more complex structure ; besides, in certain species, long 

 prolongations of the shoulder, apparently exercising a tentacular faculty : 

 and a number of branchiae, variously disposed in external arrangement. All 

 individuals are distinguished by extraordinary fertility. Much diversity, 

 according to genera and species, distinguishes the spawn ; and the young 

 of all apparently undergo a remarkable metamorphosis, in their progress 

 to maturity. 



On minute investigation, I believe, a correspondence may be found 

 between the form of the head, the structure and arrangement of the 

 branchiae, and the mode wherein the spawn is deposited. 



SECTION I. TRITONIA. Body solid, invested by a cloak. Tentacula 

 two, retractile, within sockets. Branchiae marginal, erect, palmate. 



1. TRITONIA HOMBERGII Hombcrtfs Doris. Plate XXXVIII. 



This is the giant of the race, insomuch that the naturalist, familiar 

 with the puny specimens of ordinary occurrence, can hardly persuade 

 himself, on seeing them together, that they belong to the same genus. 

 He deems its association, even with the best of the larger kind, as some- 

 what incongruous, the mass is so unwieldy. 



But the vast disproportion between the parts of kindred animated 

 beings, while the vital functions are alike effective in both, is well adapted 

 to prove the excellence of the model whereon they are framed. 



The rarity of adults having attained their full dimensions in the 

 Scotish seas, my ignorance of the quality of their food, the difficulty of 

 preservation, and the injuries of atmospheric influence, for a long time 

 embarrassed my exertions to ascertain any definite points in the history 

 of this remarkable species. Nor, in this country, will it be easy for any 

 one to counteract these obstacles, or to find a remedy. 



But we have, further, to conjoin the sluggish disposition of all the 

 tribe, doubtless extending to their native haunts ; and the exhaustion, 

 almost to the death, inseparable from the waste, concomitant on spawn- 



