UROGENITAL SYSTEM OF MYXINOIDS 125 



Along the posterior 25 or 30 mm. the mesovarium of young 

 animals has a narrow band (0.5 mm. wide) of testis lobes, as 

 shown in figure 65, but there are no traces of such testis lobes 

 in any of the nine adult females which have normal eggs. A 

 few small eggs are occasionally found in the mesovarium proxi- 

 mad to these testis lobes, but only at the anterior end of the testis 

 band. The posterior end of the mesovarium in adult females 

 with normal eggs may contain a few small eggs or brown bodies, 

 but it is usually without any reproductive elements. 



Sections were made of portions of the bands of testis lobes found 

 in two of the young animals, viz., no. 18, no. 7. Figure 75 is a 

 transverse section of the band in Myxine no. 18. The structure is 

 similar to that of the young European Myxine as described by 

 Nansen ('87), Cunningham ('87 and '92), and Schreiner ('05). 

 The testis band consists of a large mass of stroma cells and 

 many primitive germ cells which lie among the stroma cells. 

 The band is attached to the digestive tract by the continuation 

 of the mesovarium, though here it may perhaps be called more 

 properly the mesorchium. Here and there, in a transverse 

 section of the band, is a small follicle formed by a single layer 

 of stroma cells, inside of which are from four to two or three 

 dozen spermatogonia. No mitotic figm'es are present in any of 

 the spermatogonia. On the contrary, the cells are in a resting 

 stage, the nucleolus being visible in most of them. The entire 

 mass is surrounded by the squamous epithelium of the 

 mesorchium. 



Myxine no. 7 is older than no. 18, and its testis lobes are more 

 advanced in development, as is shown by figure 76. The follicles 

 are more numerous, are larger, and contain more spermatogonia. 

 The stroma cells are much less numerous. No mitotic figures 

 are present, but the chromatin of many of the spermatogonia is 

 scattered throughout the cell and the nucleolus has disappeared. 

 The epithelium which surrounds the testicular mass is thicker, 

 and here and there it turns inward, thus cutting the testis band 

 into lobes. Small eggs occur along the entire distal margin of the 

 mesorchium anterior to the testis band. The follicles of neither 

 no. 1 8 nor no. 7 contain any spermatozoa. These specimens are 



