go THE LIFE OF THE MOLLUSCA 



100,000,000 ova. A portion, supposed to be one- 

 seventh of the ovary of a Ship-worm (Teredo) was 

 estimated to contain 1,874,000 eggs. For Chiton 

 200,000 is quoted. Among Cuttlefish Loligo and 

 Sepia are said to have 30,000 to 40,000. A single nida- 

 mental ribbon of the Sea Slug (Archidoris) has been 

 reckoned to enclose 50,000 to 300,000. The single 

 capsules of Purpura lapillus — and one individual, it 

 is said, has been observed to produce 245 of them — 

 contains from 400 to 600 eggs, of which, perhaps, 

 only 10 to 16 attain maturity, the remainder serving 

 as their food while in the capsule. The Pulmonata 

 lay comparatively a small number of eggs. The 

 freshwater Limpet (A noylus) lays only 5 or 6, Limncza 

 and Planorbis 20 to 100 in each mass. The common 

 Garden Snail (Helix aspersa) produces 40 to 100. 

 The viviparous forms average fewer, Vivipara bring- 

 ing forth about 15, and the Stenogyridse about 4 or 

 6. The eggs of many of the Land Snails have a 

 regular calcareous shell, and are sometimes of great 

 size, those of the African Achatina and the South 

 American Strophocheilus (Plate XXX., Fig. 1) rivalling 

 a pigeon's egg in magnitude. 



In most cases the eggs or young are at once 

 abandoned to their fate, but in some instances a 

 partial protection is extended to them in their early 

 stages. Occasionally the eggs are attached to the 

 parent shell. This is the case in Liomesus Dalei, 

 while several species of Theodoxis and Septaria have 



