EGGS OF MARINE GENERA 



125 



They are deposited separately in clusters of from 15 to 150, tliere 

 being about 20 ova in each capsule. It appears that all the 

 species of the same genus have by no means the same method 

 of depositing their eggs, nor do they always produce eggs of at 

 all similar size or shape. Thus, of two British species of Nassa, 



Fig. 39. — Various forms of sjiawii 

 ill I'rosohranchiata : A and D, 

 I'yrula or Busycon ; B, Conus ; 

 C, Voluta miisica ; E, Ampul- 

 laria (from specimens in tlie 

 British Museum); all x % 



iJU/'kyiy> 



N. rctU'ulata lays egg-capsules in shape like Hattened pouches 

 with a short stalk, and fastens them in rows to tlie leaves of 

 Zostcra ; M. incrassata, on the other hand, deposits solitary 

 capsules, which are shaped like rounded oil-flasks. Nejjtunea 

 antupia lays its eggs in bunched capsules, like Bvxc. undatum 

 (Fig. -40), Ijut the capsules of N. gracilis are solitary. 



In Xatica the eggs are deposited in what looks like a, thick 

 piece of sand-paper, curled in a spiral form (Fig. 41). The sand 

 is agglutinated by copious mncus into a sort of sheet, and the 

 eggs are let into this, sometimes {X. heros) in regular quincunx 

 form. lantliina attaches its eggs to the under side of its float 

 (Fig. 42). The Trochidae deposit their eggs on the mider side 

 of stones and sea-weeds, each ovum being contained in a separate 

 capsule, and all the capsules glued together into an irregular 

 mass of varying size. The female of Galcrus chinensis hatches 



