PRONEOMENIA HAWAIIENSIS. 89 



bottom of this hollow are attached a group of ganglion cells that connect in turn 

 with a nerve from the postpallial commissure. Several muscle fibres are also 

 united to the base of this organ. Judging from appearances the pressure of the 

 blood beneath causes an eversion of the cells of the sensory pit bringing them to 

 the level of the general body surface while the contraction of the muscle fibres 

 produces their withdrawal and, if of sufficient strength, the overarching of the 

 surrounding spicules. 



The anomalous sense organ mentioned ])reviously as occurring slightly in 

 front of the dorsal organ proper consists of two sensory pits in all essential 

 respects like the one just described. They are separated by a ridge (Plate 32, 

 fig. 10) on which the spines are relatively small and the hypodermal epithelium 

 only slightly different from that found over the body elsewhere. Nerves from 

 the post lateral (imllial) commissure pass to the depressed area that thus appears 

 to be the sense organ proper. 



As in other Solenogastres the hermaphrodite gland is in the form of two 

 greatly elongated sacs closely appressed along the mid line and extending nearly 

 as far forward as the brain. As usual the ova are developed along the inner 

 wall while the spermatozoa are produced more externally. In the region of 

 the heart each half of the gonad becomes narrowed to a small duct that communi- 

 cates with the front end of the pericardium, which in one of the specimens was of 

 large size and filled with sex products. 



From the postero-lateral borders of the pericardium the coelomoducts 

 arise (Plate 13, fig. 4) as relatively slender tubes, and coursing forward and down- 

 ward make their way by a fairly direct course to a point near the front end of the 

 shell gland into which they open. Each canal is in the form of a greatly elongated 

 spindle lined throughout the first part of its course with low flat cells, having 

 indistinct boundaries like those of the pericardial cavity. In the middle enlarged 

 section they attain a greater height becoming nearly cubical, a shape they retain 

 throughout the remainder of this section of the genital canal. 



The shell gland or slime gland is a comparatively voluminous organ roughly 

 U-shaped in form (Plate 11, fig. 5). Anteriorly each limb communicates with the 

 spiral seminal receptacle and the section of the gonoduct just described while 

 posteriorly both unite and enter the cloaca by a comparatively narrow opening. 

 In striking contrast to the low epithelium of the dorsal limb of the genital canal 

 the lining cells of this section possess clearly defined walls, are high and slender, 

 and are glandular in character. Those in the neighborhood of the seminal 

 receptacle differ considerably in the nature of their secretion from those of the 



