No. 2.] DEVELOPMENT OF MARINE ANNELIDS. 265 



C. LEPIDONOTUS SP. 



Habits and cleavage. — The breeding season of Lepidonotus 

 at Woods Holl extends from the last of April nearly to the first 

 of June.* The adult worms are commonly found under stones 

 and mussel-beds, and are easily captured, for, when disturbed, 

 they do not attempt to escape, but roll up like porcupines, and 

 depend on their tough dorsal scales for protection. There is 

 no difficulty in separating the males and females, for the 

 former are whitish while the latter are dark on the ventral 

 surface. 



It seems that the females may carry the fully ripe eggs for 

 a long time before laying them, for nearly all those captured, 

 even early in the breeding season, can be induced to deposit 

 their eggs the day they are collected. 



In captivity the worms will rarely lay in the daytime. At 

 night, more frequently from 8 to 10 o'clock, they can usually 

 be persuaded to discharge their eggs, if they are suddenly 

 plunged into colder water, and held up close to the lamp. 



The animals remain at the bottom of the dish, and, except 

 for a slight tremor, do not move, while the eggs or sperm 

 stream in delicate threads from the eighteen pairs of nephridial 

 pores. As in the two species described above, the eggs may 

 be kept in sea-water several hours before fecundation. I have 

 fertilized eggs at 8 o'clock in the morning which were laid 

 some time during the night by isolated females, and once pur- 

 posely kept eggs in sea-water from 5 until 8.30 p.m. before 

 fertilizing them. They developed perfectly well in both cases. 



When first laid, the eggs are quite opaque, and very irregular 

 in form. They soon become approximately spherical and about 

 6 5 /A in diameter. The rapidity of development depends directly 

 upon the temperature of the water (see further on p. 269) : at 

 8° C. the eggs reach the 2-cell stage in about 2>^ hours after 

 fertilization ; the first cleavage furrow is completed in five 

 minutes and sinks in all round the eggs at the same time, and 

 not first at the animal pole, as in many eggs with abundant 

 yolk like Nereis and Clymenella. Fig. 89 illustrates the point. 



* They may breed earlier. 



