HABITS, ETC., OF CEREBRATULUS LAOTEUS. Ill 



well-known habit of all species, the lateral margins of whose 

 bodies are produced into a thin edge throughout the greater 

 part of their length. But although I have been out at night 

 repeatedlj and towed over localities where the worms were 

 abundant, I have never been fortunate enough to catch one 

 swimming. 



Frequently, however, some that were dug out of the sand 

 were thrown into the water and watched swimming about, 

 and others have often been seen swimming in the aquarium. 

 Under such circumstances the Nemertean does not turn up 

 edgewise, but undulates about in every possible position, the 

 body being now dorsal side up, now ventral, now with the 

 right side uppermost, now the left, the change from one 

 position to another being continuous though slow. It would 

 seem probable that they come out of their burrows and swim 

 about most frequently during the breeding season, although 

 eggs are laid inside the burrows, as we shall see later. 



In addition to swimming and crawling through their 

 burrows these Nemerteans are also capable of moving along 

 on the bottom over the mud or stones quite rapidly, and yet 

 as they have no setfe like the earthworm, nor any other means 

 to prevent slipping, and as the surface of their body is 

 slimy, there is always a considerable loss of motion. On a 

 solid surface the mode of progression is by crawling in a 

 manner similar to that of a Gastropod, with the exception 

 that the waves of muscular contraction, passing backward 

 from the head, are much more apparent. 



But this is true only of the adults ; young individuals can 

 glide over the glass sides of an aquarium so smoothly that 

 their bodies show scarcely a wrinkle (cf. 34). 



The Nemertean also leaves a track of mucus, like the Gas- 

 tropod. This mucus is exuded even when the animals are 

 lying coiled up at rest, and it is so abundant that a pail con- 

 taining several fresh vigorous worms is soon filled with a 

 perfect meshwork of mucus, from which the worms must be 

 pulled or cut out. And it acquires sufficient consistency to 

 offer considerable resistance. If it be removed it is quickly 



