167 



size. In transverse section it appears as an elliptical structure with 

 the long- diameter approximately parallel to the penial invagination. 

 The greater part of the cntal surface of the organ is covered with a 

 well-developed musculature which is a continuation of the circular 

 muscle layer of the body wall. The body of the bulb is composed of 

 cells of one kind, which have their enlarged nucleated parts near the 

 periphery and each of which sends a long process in an ectal direction. 

 These prolongations lie parallel to each other, and the majority of 

 them end radially around the penial lumen. Others end on the ectal 

 surface ventrad to the penial pore. The sperm duct unites with the 

 bulb on the ectal surface. In the retracted state the penial lumen 

 shows a very decisive bend of about 120 degrees before it opens into 

 the invagination. None of the specimens examined showed the bulb 

 in the everted condition. Many of the preparations showed a break 

 or cleft in the body of the bulb which conformed in direction to the 

 long diameter and, in a single section, appeared to separate the 

 nucleated ends of the cells from the greater part of the cell prolonga- 

 tions. 



Spcniiatheccc. — Each spermatheca (PI. XII, Fig. 50) consists of 

 two clearly differentiated parts, the ampulla and the duct. The am- 

 pulla is simple, pear-shaped, and has no diverticula. Its inner end is 

 united with the latero-dorsal part of the digestive tract in the pos- 

 terior part of V. The cavity of the ampulla conforms in general to 

 the shape of the exterior. The walls are rather thin except at the 

 ectal end, where they are conspicuously thicker. The duct extends, 

 with very few curves, to its external opening in the anterior part of 

 V. There are no glands at the ectal opening. The duct is about 

 twice as long as the ampulla. The external hypodermis surrounding 

 the external opening of the duct is distinctly thickened. 



ENCHYTR^US Henle 



The genus Bnchytrccus was established by Henle in 1837, and al- 

 though the limits of the group have been altered from time to time 

 it appears to have a permanent place in the family. Michaelsen ('00, 

 p. 88) defines the genus as follows : "Borsten in 4 Biindeln, 2 ven- 

 tralen und 2 lateralen, gerade, die eines Biindels gleich lang. 

 Kopfporus klein, dorsal zwischen Kopflappen und i. Segm. ; Riicken- 

 poren fehlen. Ursprung des Riickengefasses postclitellial ; Blut meist 

 f arblos ; Herzkorper fehlt. Lymphkorper von einerlei Gestalt. 

 Peptonephridien vorhanden oder fehlend ; der Oesophagus geht all- 

 mahlich in den Mitteldarm fiber. Ausfiihrungsgang der Nephridien 



