UROGENITAL SYSTEM OF MYXINOIDS 105 



advanced (fig. 41). As this figure shows, one large blood sinus 

 has appeared in the glomerulus. This sinus contains corpuscles 

 and blood plasma, and extends almost the entire length of the 

 glomerulus. It has an epithelial lining, outside of which are sev- 

 eral concentric layers of connective tissue. On the opposite 

 side of the glomerulus there is a large space with comparatively 

 few nuclei, but entirely filled with slender fibers of connective 

 tissue. This space also extends almost the entire length of the 

 glomerulus. The lining of Bowman's capsule is an epithelium 

 surrounded by a broad band of concentric layers of connective 

 tissue. 



In one Bdellostoma and one young Myxine the glomerulus of 

 the pronephros is double ; two distinct glomerular masses are con- 

 tained in the same Bowman's capsule. In the Bdellostoma the 

 capsule is constricted to one-half its width at the point of union 

 between the two glomerular masses, while in the young Myx- 

 ine there is but a slight constriction in one side of the capsule 

 (fig. 42). 



In all the pronephroi of both animals, one or more pronephric 

 tubules open into the cavity of Bowman's capsule of the Mal- 

 pighian body. The capsule in every specimen of Bdellostoma is 

 connected with the pericardial cavity by a more or less long, very 

 narrow duct (approximately one-half as wide as a pronephric 

 tubule). In addition to this duct there may be one or more 

 very small openings through the wall of the capsule which con- 

 nect the cavity of the latter with the pericardial cavity. The' 

 capsule of the specimen represented by figure 12 has seven such 

 openings. In none of the specimens of Bdellostoma are these 

 openings into the pericardial cavity greater than two or three 

 one-hundredths of a millimeter in diameter. 



Spengel ('97) considers the glomerulus of the pronephros to 

 be really a glomus because it hangs freely in a cavity which he 

 found communicated with the pericardial cavity through a very 

 large aperture; in one specimen the opening extended through 

 nineteen sections each 30 microns thick, or 0.57 mm. Semon 

 ('97) never saw in his preparations a communication as wide as 

 Spengel described. Maas ('97) also considers the glomerulus a 



