140 BULLETIN OF THE 
laboratory, which is located on a small cove near the mouth of Narra- 
gansett 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 @. 
By the first kind of motion it makes rapid and definite progress ; but 
the purpose of the latter did not seem to be locomotion ; 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, | 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 
