164 G. A. and W. G. MacCallum, 



must regard as the sliell gland. Tliis gland is developed to a very 

 great extent probablj' because of its task of furnishing shell material 

 to the myriads of eggs which collect in the uterus. The combined 

 Channel twists about as a very narrow canal through a great deal 

 more of the shell gland and finally emerges toward the posterior 

 end as a gradually wideniug tiibe filled with eggs which are at 

 first small and polygonal and do not show perfectly their completed 

 form nor their finished shell. It is only after many coils that the 

 eggs assume their definitive appearance. The course of the uterus 

 after tliis has been described. In this species it nowhere becomes so 

 bulky as to distort the cylindrical form as described by Maclaren 

 for N. molae. It opens on a little hillock just behind the mouth 

 sucker and the terminal portion though surrounded by a few nucle- 

 ated cells resembling those of the skin is not provided with any 

 special musculature. The testis is Single though much folded and 

 twisted in its posterior part. It begins anteriorly as a sausage- 

 shaped structure at about the poiut where the neck of the w^orm 

 begins to widen out into the body and runs backward for a distance 

 of only about two or three millimeters. Anteriorly it gives otf a 

 convoluted vas deferens which runs beside the uterus to practically 

 the same point just behind the mouth sucker. There it dilates a 

 little into a bulbous extremity wiüch then narrows to pass into a 

 pear shaped sac which opens again on the apex of a little hillock. 

 This sac has at most a delicate layer of circular muscle fibres 

 surrounded by a number of closely arranged deeply staining cells, 

 but it is lined by a layer of stiff recurved hairs. It can probably 

 be everted to act as a penis. The testis shows a compact outer 

 layer of cells but in the inferior the cells are grouped in Clusters 

 separated here and there by sheaves of straight rigid spermatozoa. 

 There seems to be some indication of a Separation of the sexes 

 in this form, for although each worm possesses both male and female 

 Organs in füll development as far as can be seen from study of the 

 testis, ovary, shell gland etc. the terminal portion of the uterus with 

 the uterine outlet is well developed and conspicuous in one of the 

 pair but scarcely traceable in the other. On the other band the 

 vas deferens with its bulbous seminal reservoir and the sac which 

 serves as a penis is very striking in the other worm of the pair 

 while in the first one in which the uterine opening is so evident 

 110 such sac can be found nor can the vas deferens be definitely 

 traced to an outlet. It is quite empty of spermatozoa in its cephalic 



