PRONEOMENIA HAWAIIENSIS. 87 



Upon reaching the front end of the cloacal passage (sHme gland) (Plate 14, 

 figs. 5, 6) the alimentary canal becomes crescent-shaped in cross section, the 

 concave surface being in contact with the gonad. Before reaching the cloaca 

 it becomes elliptical and the epithelial lining is developed into longitudinal 

 folds that persist to the anal opening. 



The heart is irregularly cylindrical in form, lacks any clear subdivisions and 

 is attached to the dorsal wall of the pericardium. From its anterior end the 

 dorsal aorta takes its origin and coursing forward between the gonad and the 

 body wall finally makes its way into the roughly defined head cavity. At 

 irregular intervals it gives rise to small ventral branches that pass between the 

 halves of the reproductive gland and enter a sinus lying along the under side of 

 the organ. From this vessel lateral branches extend around the sides of the 

 gonad and open into the visceral cavity dorsally. This relation of aorta and 

 gonad continues as long as any trace of the latter exists, and anterior to this 

 point the aorta gradually enlarges and finally in the neighborhood of the brain 

 passes into the "head cavity." This last named space is not bounded posteri- 

 orly by a septum, but is well defined by the front end of the pedal gland through 

 and around which the blood passes backward by small channels into the visceral 

 cavity proper. This large sinus surrounding the digestive tract is subdivided 

 into two roughly defined spaces, a relatively large sinus lying beneath the in- 

 testine and a very much smaller one located between it and the foot. At irreg- 

 ular intervals these two communicate and small lateral canals also connect the 

 pedal sinus with the main section of the visceral cavity. The latter also com- 

 municates with the ventral intestinal sinus by fairly well-defined lateral canals 

 that occupy positions between the gut. pouches. In the neighborhood of the 

 cloacal passage these minor sinuses unite with the larger and the blood, that has 

 travelled backward in all of them, makes its waj' dorsally to open into the hinder 

 end of the heart. 



In a foregoing account (Heath '04) the nervous system of this species has 

 been described and in this connection it is only necessary to mention the more 

 prominent features. As is represented (Plate 5, fig. 2), the brain is situated in a 

 depression immediately in front of the dorsal salivary glands. Anteriorly it 

 develops six nerves whose branches supply in large measure the sense organs 

 of the buccal wall and probably the hypodermis and the musculature of adjoin- 

 ing regions. Posteriorly it gives rise to three pairs of nerves, the lateral, pedal, 

 and labio-buccal connectives. The lateral cord almost immediately takes up 

 its permanent position at the sides of the body ; the pedal passes downward and 



