.122 INTRODUCTION TO ZOOLOGY CHAP. 



They are laid in little horny capsules, which are fused together 

 in a sponge-like mass, often in clusters of a hundred or more. 



Each capsule contains 500 to 600 

 eggs, but only a small number of 

 these develop. The eggs are laid 

 in the autumn, but the little larvae 

 do not leave the egg-case until the 

 spring. They are able at first to 

 swim freely in the water. 

 FIG. l&.Bucdnum MI datum. Nassa reticulata, the 



A small Cluster of Egg Cap- Nassa, The D W} lp ll, ma , T V>P 

 sules. Dog Whelk. JJo o VvnelK, may be 



found near low tide 



mark crawling over the rocks or sand at the bottom of the 

 water, or completely buried in the sand except for its waving 



FIG. 77. -The Dog Whelk (Nassa reticulata). 



A, Crawling over the bottom of a rock pool ; 7)', at rest, partly buried in the sand ; 

 E, eggs attached to a stalk of seaweed. 



respiratory siphon. The broad yellow foot is speckled with 



black, and has a small horn-like process on each side of its 



broad front end and two small pointed "tails" at the back end. 



The Cowry is another carnivorous gill-breath- 



The^owrv * n & mar ^ ne snail, the shell of which is very 



thick and hard ; the mantle is reflected for some 



distance up each side of the shell (Fig. 78). 



The genns Murex is interesting because of the 

 Spiny Murex, the Mediterranean species, from the 



