METAMORPHOSIS. 373 



very different form of the adult state. We have succeeded 

 in bringing out the larvge of Doris, Tritonia, Melibcea, and 

 Eolis, between all of which there is a very great resem- 

 blance." * 



On comparing the larva with the adult Mollusk, we find the 

 following differences: it has a nautiloid shell (Fig. 77, a); 

 and in lieu of tentacula, it has two veils, shaped somewhat 

 like ears, and which empower it with rapidity of movement 

 (Fig. 77, 6). These veils disappear at a later period, and 



Fig. 77. 



leave no trace of their existence. Destined to feed on soft 

 infusorial animalcules, the larva has as yet none of the 

 complicated oral organs of the adult ; and the stomach 

 is situated much further backwards in the body. The 

 branchiae and the digestive cceca are wanting ; while the 

 existence of an operculum necessitates that also of a peculiar 

 muscle to attach and govern it. The eyes, the ears, the 

 liver on the left side, and the anus on the right, are as in 

 the adult. 



How long the larva remains in the first stage is still 

 unascertained. Arriving at the second stage, we find it still 

 enclosed in its shell, but the mantle has become detached 

 and covers tightly the mass of the viscera. The foot is so 

 enlarged that it forms a considerable projection beyond the 

 margin of its operculum ; and the veils have also grown in 

 size, while the eyes have altered to a violet colour. The 

 head has now two short conical ciliated tentacula ; and the 

 little animal swims with surprising quickness. 



* Rep. Brit. Assoc. 1844, p. 27. Also Ann. and Mag. N. Hist. xii. 235. 

 Monogr. Brit. Nudibr. Moll. ii. pi. 1, fam. 3. 



