MUSEUM OF COMPARATIVE ZOOLOGY. 139 



gus is lined by a minute chitinous tube, which is intracellular in position, 

 and after forming a loop opens out into an intercellular intestine that is 

 highly degenerate posteriorly and in the adult lacks a terminal opening. 

 The posterior end of the male is a ventrally curved conical mtromittent 

 organ with a terminal opening. The female is provided with a terminal 

 bulb having a central cloacal (?) opening. The small spherical eggs are 

 filled with large refractive yolk granules and protected by a shell, the 

 thickenings of which become long and pointed spines on coming in con- 

 tact with the water. The eggs measure 36-40 fi in diameter without 

 the spines, which are 8 to 10 /* long. Color of the animal in life gray- 

 ish to yellowish white with transparent anterior end. The median lines 

 each show two narrow longitudinal bands of dark slate color. 



Length of the male, 50 to 200 mm. ; of the female, 30 to 60 mm. 

 Diameter, 0.3 to 1 mm. 



Habitat : Narragansett Bay, R. I., A. Agassiz (1870-90), J. W. 

 Fewkes (1883); Vineyard Sound, Mass., S. I. Smith (1871), A. E. Verrill 

 (1879); Wood's Holl, Mass., W. M. Woodworth (1888), E. A. Andrews 

 (1890). 



III. Biology. 



Up to the present time Xectonema has been reported from two places 

 only, Newport, E. I., and Wood's Holl, Mass., and the south shore of 

 New England may fairly be considered as its home. Here it is not so 

 rare as has been supposed, for by systematic search fifteen specimens 

 were secured in one summer. The dates of capture of some sixty-five 

 specimens show that it may be found from the last of June to the first 

 of October,^ with two maxima, one in July and a second in September, 

 more than two thirds however having been caught at the earlier date. 

 It is noteworthy that, of the fifteen individuals captured at Newport last 

 summer, all were taken while the tide was going out, and on evenings 

 when there was no moon, the ordinary time of towing being between 

 8 and 10 p.m. The latter circumstance seems to indicate that the 

 worms are susceptible to light ; the possible significance of the former 

 will be discussed later. It is also an interesting fact, that they were 

 caught in towing near the shore, two in fact having been dipped up one 

 evening in July when filling a pail with water at the landing of the 



^ I do not believe that towing has been done in this region with any regularity 

 at other times of the year, so that tliese dates cannot be accepted as fixing the 

 time of its occurrence 



