400 TREADWELL. [Vol. XVII. 



have been completed. In the preparation of my drawings I 

 am indebted to my wife, who has finished from my camera 

 sketches all of the figures which illustrate this paper. 



Podarke obscura is a small Hesionid, abundant in various 

 localities at Woods Holl, Mass. The species was described 

 and named by Verrill (No. 30), who says that at night during 

 July and August they come to the surface and swim about "in 

 vast numbers." I have never been able to confirm the latter 

 observation and have found only a few when towing at night, 

 these seeming rather to be attached to bits of floating eelgrass 

 than swimming free. In the "Eel Pond" and in "Little 

 Harbor" they are abundant, lying in the soft, flocculent sur- 

 face mud and clinging to the eelgrass a short distance from 

 the bottom. It is almost hopeless to attempt to pick the 

 animals from the mud, and I have found the best way to collect 

 is to sweep through the grass with a strong net. (I used 

 for this purpose a wooden-rimmed flour sieve.) The animals 

 remain in the sieve and can easily be jarred into a bucket, 

 while the finer dirt passes through with the water. They were 

 then transferred to clean water in glass dishes in the labora- 

 tory, where with only an occasional change of water they will 

 live indefinitely. Both in their natural environment and in 

 captivity they seem rather sluggish, though if irritated they 

 will swim rapidly away from the disturbing object. They will 

 burrow quickly into any dirt or sediment that may be in the 

 dish, but seem in no way inconvenienced if forced to live in 

 clean water. The occurrence of bifid monsters is very com- 

 mon, a number of such cases having been described by 

 Andrews (No. i). 



Specimens in captivity lay their eggs from 7.30 to 9 p.m., 

 usually on the second or third, rarely on the first, night after 

 they are brought into the laboratory. The eggs have no albu- 

 minous coat, and hence when extruded sink rapidly to the 

 bottom of the dish, where, if the water be clean, they may 

 easily be recognized and picked out with a pipette. A simpler 

 expedient is to strain the water through a fine cloth, through 

 whose meshes the eggs will pass, leaving the adult annelids 

 behind. 



