STROPHOMENIA TRIANGULARIS. 127 



From transverse sections it appears that there are fifteen rows of teeth whose 

 general form is shown (Phite 34, fig. 4). They are thin and dehcate, or at all 

 events are not easily displaced in sectioning, and stain readily in haematoxylin. 



As usual with this genus the anterior intestinal coccum is of great length 

 and considerably in front of its union with the pharynx exhibits most of the 

 essential characters of the stomach-intestine, possessing fairly regular out- 

 pouchings and an epithelial lining of the customary glandular type, but lacking 

 the cubical ciliated cells beneath the gonad. The coecum and most of the suc- 

 ceeding portions of the gut contain nettle and germ cells extracted from the host. 

 Opposite the seminal receptacles the intestine narrows, becoming gradually 

 smaller until it opens into the cloaca (Plate 18, fig. 10). At the same time the 

 dorsal ciliated epithelium gradually extends round the sides of the rectum, 

 finally meeting in the mid ventral line shortly in front of the anal opening. 



The pericardial cavity in this species is of very large size and the heart of 

 unusual length. The posterior division, however, is unusually small and jieculiar 

 in being paired, save at its junction with the ventricle with which it conununi- 

 cates by a single small pore apparently furnished with a valve. The aorta, at 

 its origin, is of the same calibre as the ventricle and occupies the entire though 

 narrow space between the halves of the gonad. The branches, passing from it 

 around the ventral and lateral surfaces of the gonad to unite with the visceral 

 cavity, are likewise of large size and very distinct. More anteriorly these 

 branches become much smaller and in the I'cgion of the head all but disappear 

 in the present specimen. The course of the sinuses in the head, their union 

 with the ventral sinus and the relation of the latter vessel with the heart are 

 typical. The corpuscles are more than usually compact, but in their ellipsoidal 

 form resemble those of other species of the genus. 



The gonad extends as far forward as the radula and presents the usual 

 features. Posteriorly it opens, in both specimens examined, by unusually large 

 ducts into the pericardium, owing possibly to the fact that the time the animals 

 were killed ova were present in considerable numbers in the pericardial cavity 

 and along the cloacal passages. These canals, arising typically from the poste- 

 rior end of the pericardium (Plate 9, fig. 3), average approximately 0.095 mm. 

 in diameter and are lined with cubical and low columnar richly ciliated cells. 

 Toward the median line of the body these elements are more glandular and the 

 secretion may direct the course of the sperms. 



The seminal receptacles, numbering 10-12, vary in size as may be seen 

 (Plate 9, fig. 3), and possess unusually long stalks. Both vesicle and duct are 



