HALOMENIA GRAVIDA. 147 



The cuticle, surrounding the body, is of average thickness (Plate 32, fig. 4), 

 but is actually rather scant in amount owing to the large numbers of spicules 

 (Plate 22, fig. 13) imbedded in it and to the papillae many of which are of unusual 

 size. On the ventral side of the body the unmodified hypodermal cells, those 

 which are probably largely responsible for the development of the cuticle, are 

 comparatively few in number and are crowded between the bases of the papillae, 

 but dorsally they become more numerous and may be seen to possess a cubical 

 form and no especially noteworthy features. Owing possibly to differences in 

 age the papillae vary greatly in size but all are constructed on essentially the 

 same plan. As may be seen (Plate 32, fig. 4) the stalk is composed of an out- 

 pushing of hypodermal cells and is usually shorter in the larger papillae. It is 

 surmounted by the usual balloon-shaped group of cells, which certainly number 

 not less than one hundred in the larger organs. Each cell is greatly elongated, 

 vacuolated in its outer portion in preserved material, and contains a spindle- 

 shaped, basally placed nucleus. In several cases the cavity of the stalk is 

 traversed by a delicate fibre, sometimes enclosing a nucleus, which appears to 

 be a nerve. 



In this species the stomach-intestine is related in a remarkable way to the 

 cuticle and papillae but for what purpose I cannot say. On the dorsal surface 

 of the smaller specimen and in the region traversed by the mid gut there are not 

 less than twenty pairs of small rounded knobs of light yellow color, forming one 

 longitudinal line on each side of the mid line. These are not distinctly visible 

 in surface views of the larger individual, but in sections they are seen (Plate 22, 

 fig. 1) to be evaginations of the dorsal wall of the intestine which protrude 

 through definite openings in the somatic musculature and extend half way to the 

 outer surface of the body. Each is in contact with the under surface of a circular 

 disc-like patch of hypodermal cells having the appearance of a modified papilla. 

 The stalk is absent and the cells are relatively low, but some are distally vacuo- 

 lated and are not the compact, cubical elements of the unmodified hypodermis. 

 Surrounding the point of attachment of gut and papilla is a small ring-shaped 

 blood sinus, frequently containing corpuscles. The relations of these various 

 elements are represented in a typical condition in Plate 32, fig. 5. Concerning 

 their mode of operation it appears probable that the pressure of the blood in the 

 sinus causes a protrusion of the papillae and the attached liver lobe, but for what 

 possible reason I cannot say. 



The spicules, whose general shape is shown (Plate 22, fig. 13), are of various 

 sizes in a mature condition even in the same locality. These are intermingled 



