4O WESLEY R. COE. 



a net which may be lowered to their habitat. The males are 

 thereby drawn to the surface and collected. Second, the very 

 conspicuous appendages of the males would direct attention to 

 them as unusual objects and they would be carefully preserved 

 by the inexperienced collector and some of the specimens are 

 known to have been obtained in this way while the closer 

 resemblance of the females to other common species of nemer- 

 teans would seem to give them a lesser importance. And, 

 finally, it seems very possible from such meager descriptions as 

 Joubin ('06) gives of six supposedly new species of Planktone- 

 mertes that one or more of them may actually be females of 

 species of Nectonemertes, for they come from the same general 

 region of the North Atlantic Ocean; that is, from stations west 

 of the Azores only a few degrees apart. With these and perhaps 

 other considerations in mind it is not surprising that more males 

 than females of the various species are known. 



Gonads. The two sexes in Nectonemertes are distinguished 

 not only by the tentacles characteristic of the males but also 

 by the position and appearance of the gonads. The spermaries 

 of the male (Fig. i) are limited to the head region, while the 

 ovaries of the female are situated in their primitive positions 

 between the intestinal diverticula along the sides of the body 

 (Fig. 2). The general appearance of the two sexes thereby 

 becomes so strikingly different that their original separation into 

 different genera is hardly surprising. 



Tentacles. Microscopic study of the tentacles of Nectonemertes 

 shows that they represent slender outgrowths of the body walls ; 

 the integumentary, basement, and muscular layers being the 

 same in both. The muscular layers, however, assume a direction 

 at right angles to those of the body, and are of far greater thick- 

 ness. The central part of the appendage is filled with an exten- 

 sion of the body parenchyma, with blood lacunae of large size, 

 and two very large nerves which originate from several branches 

 of the lateral nerve cord at points near the base of the tentacle. 



The structure of the tentacles indicates clearly that these 

 organs are capable of a high degree of muscular contraction. 

 The filamentous character of their terminal portions when well 

 developed suggests that they are not simply locomotor organs, 



