i] THE STRUCTURE OF CONVOLUTA 13 



they may be seen lying in rows in the bodies 

 of "ripe females," that is, animals in the female 

 stage (Fig. 4, b, E). The eggs are fertilized in the body, 

 though the spermatozoa which eifect fertilization 

 are derived from another individual of the same 

 species. After fertilization, the eggs are discharged 

 in groups or clutches of from about eight to fifteen 

 or more. As it is extruded from the body the 

 egg-clutch becomes surrounded by a transparent, 

 mucilaginous, sticky capsule secreted by the glands 

 on the surface of the skin. A clutch of eggs of 



Fig. 5. Egg-capsule of Convoluta paradoxa. Each egg is contained 

 in an egg-membrane and the group of eggs is enclosed by a 

 common capsule. (Magnified twenty times.) 



C. roscoffensis is recognisable to the trained eye as 

 a minute, more or less transparent sphere of about 

 the size of a small pin's head. The egg-clutch of 

 C. paradoxa is of a similar size ; but, owing to the 

 presence of pigmented granules, it is of a rufous 

 colour (Fig. 5). 



C. roscoffensis lays its eggs on the beach just 

 beneath the surface of the sand : C. paradoxa deposits 

 them on the fine sea-weed lower down the shore. 



