140 BULLETIN OF THE 



laboratory, which is located on a small cove near the mouth of Narra- 

 gaiisett Bay. 



When first caught they were very active, swimming vigorously from 

 side to side of the vessel into which the tow was emptied, and trying 

 alternately the surface and the bottom of the water. Their motions are 

 of two kinds ; first, a rhythmical movement, evidently caused by pro- 

 gressing waves of muscular contraction alternating on the two sides of 

 the animal ; and, secondly, a more violent motion, which consists in first 

 coiling the body into two large successive loops, and then straightening 

 it suddenly and coiling it at once in the opposite direction. In this 

 way the worm assumes much the general appearance of a figure 00. 

 By the first kind of motion it makes rapid and definite progress ; but 

 the purpose of the latter did not seem to be locoviotion ; it was rather 

 relief from some irritation, which on one occasion was apparently a mass 

 of foreign matter which had accumulated on the bristles. These, to- 

 gether constituting what has been called the lateral fins, can ordinarily 

 be easily seen even during the motion of the animal, and evidently are 

 not actively concerned in its movements. 



Nectonema always swims with the translucent end, which, as will be 

 seen later, is the head, in advance. How long, the activity exhibited at 

 first persists, I do not know. The animals captured in the evening were 

 usually found on the following morning resting on the bottom of the 

 dish, and exhibited only occasional fits of activity. This may have been 

 due to the effects of light or of captivity. I am inclined to consider it 

 to be the result of the latter, since usually before noon of the first day 

 after capture the worms voided into the water masses of eggs or sper- 

 matozoa which were often unripe, and then became more and more 

 sluggish. But the material was too valuable to warrant the risk of its 

 becoming injured for histological purposes by longer delay, and observa- 

 tions were therefore terminated at this point by killing the animals. 



, IV. General Morphology. 



1. External. 



Nectonema is in life of an opaque grayish white with semi-transparent 

 ends. The body is perfectly round and the median lines show no trace 

 of the flattening described by Verrill and Fewkes, and so often seen in 

 the preserved specimen. This condition is unquestionably the result of 

 collapse. The general surface of the body is smooth, except for the many 



