STROPHOMENIA REGULARIS. 117 



sheath 0.157 miii. iii tliickiiess on the side of the body. The hypodermis is very 

 well preserved but presents no unusual features. Here and there, especially 

 at the bases of some of the papillae, it contains cells, sometimes arranged in 

 groups of three, staining darkly and apparently glandular though no trace of 

 any outlet is evident. The spicules retain their connection with the matrix 

 cells as long as they are imbedded in the cuticle (Plate 24, fig. 7). The enlarged 

 portions of the papillae are relatively small, closely crowded together at the 

 surface and are attached to the hypodermis by clearly defined stalks containing 

 a few spindle-shaped nuclei. 



A well-defined dorsal sense organ is present, apparently of the usual type 

 though the oblique direction of the sections makes it somewhat difficult to de- 

 termine its exact relations. 



The foot is comparatively small, moderately ciliated, without any cavity, 

 and extends to the cloaca. It is accompained by the usual glands whose appear- 

 ance and relations are shown (Plate 24, figs. 9, 10). 



The stomach-intestine presents the customary pouched appearance, and 

 is lined with the ordinary glandular epithelium, changing to almost cubical 

 ciliated elements beneath the gonad. Nettle cells of some coelenterate host 

 are distinguishable in the small amount of material in the digestive tract. In 

 the neighborhood of the front end of the pericardium the intestine narrows, 

 becomes ciliated throughout, more or less rectangular in cross section then passes 

 into a more tubular division which in its terminal section again expands and 

 opens together with the gonoducts into the cloacal cavity. 



As may be seen (Plate 24, figs. 9, 10) the pericardium in this species is of 

 considerable size, and the presence of numerous muscle fibres passing from its 

 walls to those of the body indicates that it probably undergoes considerable 

 variation in this respect, probably while driving the sex products into the gono- 

 ducts. The heart, distended with blood, is a well-developed organ and com- 

 prises two divisions, an auricle and ventricle presumably. The walls of the 

 auricle are somewhat more dense than those of the ventricle but otherwise their 

 relations to the incurrent and excurrent blood streams are of the well-known 

 type. The blood corpuscles are represented (Plate 24, fig. 14). 



In its general relations the posterior portion of the nervous system resembles 

 that of other .species of the genus (Plate 26, fig. 8). The pedal cords, connected 

 by numerous commissures, continue of about the same calibre until they reach 

 the region of the cloaca. Here they enlarge very slightly, give rise to two or 

 three strong connectives and as many smaller commissures, and then gradually 



