104 CHAS. B. WILSON. 



registers many degrees below zero, we may conclude that 

 Cerebratulus has at least become well acclimated. 



This species burrows in sand and mud between tides, and 

 in shallow water down to several fathoms in depth. 



It occurs most plentifully at and just above low-water 

 mark, but may be found under stones in sheltered positions 

 (Quohog Bay), nearly up to the high-water mark of medium 

 tides. It is gregarious in habits, and the finding of one is a 

 good indication that there are others in the immediate 

 vicinity. It also occurs in the same localities year after 

 year, but after prolonged search in any one place the number 

 of large specimens becomes very sensibly diminished. The 

 largest specimens are not solitary, as Mcintosh declares to be 

 the case with the great Lineus marinus (34), but they are 

 so limited in numbers as to warrant the conclusion that here, 

 as in some of the higher forms of life, size is " inimical to 

 profusion." One of its favourite haunts is along the edges of 

 an old mussel-bed amidst the broken shells and stones, into 

 which it is often almost impossible to drive a clam-hoe. But 

 it is also dug up with clams in clean white sand and mud, and 

 is known locally to the fishermen as a '^ clam-worm." 



Scarcely a trace of the worms save the entrance to their 

 burrows can be seen except at high tide. This is their 

 period of activity, and they may then occasionally be ob- 

 served gliding amongst the sea-weed on a muddy or sandy 

 shore, or in the shade of the rocks in a large tide-pool. They 

 are essentially nocturnal, and come out of their burrows much 

 more frequently during the night tides than during those 

 which occur in the day time. The burrow itself is little more 

 than a hole or tubular opening through which the worm can 

 move freely in either direction. The walls of this tube are 

 coated thickly with the slimy mucus exuded from the worm's 

 skin, which materially facilitates its progress. 



The burrows are neither very long nor very deep, for even 

 the largest worms are found within a few (six or eight) inches 

 of the surface. There is no evidence to show that the same 

 burrow is inhabited for any length of time. On the contrary, 



