HABITS, ETC., OF CEREBRATTJLCTS LACTEUS. 129 



Fortunately the burrow occupied by the female was in 

 contact with the side of the aquarium, and the whole process 

 could be watched through the glass. It was seen that the 

 contents of a very limited number of genital pouches near 

 the anterior end of the body were being emptied. The eggs 

 were assisted in their passage through the oviduct by a con- 

 traction of the circular muscles of the body-walls over the 

 area occupied by the pouches. When first issuing from the 

 body the eggs were gathered in loose bunches, held together 

 by the gelatinous tissue already described. These bunches 

 were pushed along gradually by successive waves of muscular 

 contraction in much the same way that the ring of mucus 

 formed by the earthworm in egg-laying is worked off the 

 forward end of its body. 



In this way the eggs came to lie at the bottom of the 

 vertical portion of the burrow around the head of the Nemer- 

 tean. Here the action of the water quickly dissolved the 

 gelatinous material that held them together, and left them 

 free. They were then caught in the current generated by 

 the Nemertean's breathing, and carried upward out of the 

 mouth of the burrow and some distance away from it. Eggs 

 were laid in this manner several times, and upon them were 

 verified all the phenomena of maturation and segmentation 

 derived from artificially fertilised eggs. But in so restricted 

 a space there was always a tendency to over-fertilisation, and 

 many of the eggs were killed in this way. Whenever a con- 

 siderable number were laid at once they collected together at 

 the bottom of the aquarium, and were held together loosely 

 by adhesion of the zonae pellucidae, but a slight disturbance 

 in the water separated them and they floated away free. 



Nothing could be seen of the burrow occupied by the male 

 except its opening, but as sperms were issuing from this in 

 the same way that eggs were from the other, and as a thick 

 mass of sperms was afterward found at the bottom of the 

 burrow in a position corresponding to that of the eggs, it would 

 seem safe to conclude that the sperms are discharged in the 

 same way as the eggs. 



VOL. 43, PAUT 1. NEW SKRIES, J 



