UROGENITAL SYSTEM OF MVXINOIDS 113 



the distal ends of the epithelial cells, especially in the large 

 cells of the ridges, is suggestive of secretion. 



The envelope of connective tissue surrounding the duct con- 

 sists of two parts, a loose web containing blood vessels and a 

 more or less compact stratified layer. The loose web lies next 

 to the basal membrane of the epithelium. It follows closely 

 the outline of this membrane, and fills the concavities under the 

 ridges, as shown in figure 53. Some of the blood vessels in this 

 connective tissue contain giant blood corpuscles, like those 

 found in the central mass. 



The compact stratified layer consists of fibers arranged in 

 concentric rings around the duct, and is usually thicker along 

 the median surface of the duct. The peritoneum Ues next to 

 the stratified layer. 



The writer was unable to identify in Bdellostoma the three 

 layers which W. Muller describes as forming the connective 

 tissue envelope around the duct of Myxine. Nowhere is there 

 a layer that can be called the 'membrana propria.' The two 

 layers observed by* the writer correspond to the ' adventitia' 

 and the layer which contains blood vessels, as designated by 

 Muller. 



Malpighian bodies. Price has shown that at one time in the 

 development of Bdellostoma the mesonephric duct is continuous 

 with the central duct of the pronephros, but that, later, a short 

 piece of the duct posterior to the pronephros degenerates, to- 

 gether with its Malpighian bodies. The amount which degener- 

 ates is not always the same, hence in the adult there is consider- 

 able variety in the structure of the anterior ends of the ducts 

 and in the location of the first few Malpighian bodies of the 

 mesonephros. The most anterior Malpighian body of the 

 Mesonephros may be located immediately posterior to the Mal- 

 pighian body of the headkidney and may be attached to the 

 latter and to a short, isolated piece of the mesonephric duct 

 (fig. 12) ; or it may be completely isolated in the space between 

 pro- and mesonephros. Not only one, but two or three of the 

 mesonephric Malpighian bodies may be in the intermediate space, 

 entirely disconnected from each other and from the mesonephric 



JOURNAL OF MORPHOLOGY, VOL. 29, NO. 1 



