UROGENITAL SYSTEM OF MYXINOIDS 127 



length of the mesorchium (fig. 83). Specimen no. 12 has the 

 general appearance of being older than no. 13. At the anterior 

 end of the genital fold the width of the mesorchium and the 

 testis band together is 4 mm., and it increases at once to 5 mm., 

 then fluctuates between 4 and 5 mm. to a point about 7 cm. 

 from the extreme posterior end. At this point the combined 

 width of the band and the mesorchium increases to 7 mm. and 

 remains this to the posterior end of the mesorchium. The testis 

 band is suspended from the distal end of the mesorchium, and 

 at the anterior end it is 1 nam. wide by 0.5 mm. thick. The 

 band increases gradually in both width and thickness as it pro- 

 ceeds posteriorly, and at mid-region it is 2 mm. wide by 0.75 

 mm. thick. At a point 7 cm. from the posterior end it reaches 

 its maximum size, 6 mm. wide by 1 mm. thick, and retains these 

 dimensions to the extreme posterior end, immediately in front 

 of the genital pore. The testis band of specimen no. 13 is neither 

 as high nor as thick as that of no. 12, the widest part being 5 

 mm. Also, it is not as lobulated as the band of no. 12, and it is 

 yellowish in color instead of reddish as in no. 12. In the latter 

 the small lobules give a gi-anular appearance to the band, which 

 is especially pronounced in the posterior region. There is not 

 the slightest trace of eggs, normal or degenerated, at any place 

 in the mesorchium of either no. 12 or no. 13. Myxine no. 12 is 

 67 cm. and the testis band is 36 cm. long. Specimen no. 13 is 

 63 cm. long and its testis band measures 35 cm. 



Transverse sections, cut in all parts of the testis bands of these 

 two animals, reveal the fact that the bands are of uniform and 

 peculiar structure. They do not resemble the testis bands of 

 younger Myxine, nor those of Bdellostoma, as figures 80 and 81 

 show. The squamous mesorchial epithelium has been completely 

 converted into the palisade layer of columnar cells. In trans- 

 verse section the band is cone-shaped, and deep notches in the 

 sides cut it into triangular lobes, leaving a central core of stroma. 

 The latter has been entirely converted into fibrous connective 

 tissue which contains many blood capillaries. Nowhere in the 

 bands is there the slightest trace of primitive germ cells or fol- 

 licles. Figure 81, a transverse section from the posterior end 



