422 



THE MICROSCOPE. 



shell. The amber-snail, Succinea amphibia, has a beautiful 

 transparent shell of a light amber colour; and it is from 



2, 



Fig. 210. 



1, Palate of Buccinum undatnm, common Whelk, seen under polarised light. 

 2, Palate of Doris tuberculata, Sea-slug. 



this that it derives its scientific name Sucdnum, amber. 

 The puddle-mud snail (Limnceus peregra) is also very gene- 



1 Fig. 211. 



1, Physa fontinalis, the Amber Snail. 2, Moor Snail and Mountain Bullmus. 



rally distributed. The shells of all the species (Limncea) 

 have the aperture on the right hand, and the plait on the 

 left hand, which distinguishes them from the Physa fonti- 

 nalis, stream-bubble shell. 



It is extremely curious to watch the development of the 

 spawn of these animals under a low magnifying power. 

 The spawn of the Water-snail is usually found adhering to 

 the surfaces of stones, pieces of weed, or other matters in 

 the water ; and generally connected together in long rib- 

 bon like delicate ova-sacs of a curious and beautiful form. 

 The mass of eggs deposited by the Doris resembles a frill 

 of lace of great beauty. In the Aplysia the spawn re- 

 sembles long strings of vermicelli, of varying tints through- 



