8 14 STRUCTURE AND DEVELOPMENT OF LEPIDOSTEUS. 



divided into a series of lobes (10 12), and were suspended by 

 a delicate mesentery (mesorchium) from the dorsal wall of the 

 abdomen on each side of the dorsal aorta. Hyrtl (No. 11) 

 states that air or quicksilver injected between the limbs of the 

 mesentery, passed into a vas deferens homologous with the 

 oviduct which joins the ureter. We have been unable to find 

 such a vas deferens ; but we have found in the mesorchium a 

 number of tubes of a yellow colour, the colour being due to 

 a granular substance quite unlike coagulated blood, but which 

 appeared to us from microscopic examination to be the remains 

 of spermatozoa 1 . These tubes to the number of 40 50 con- 

 stitute, we believe, the vasa efferentia. Along the line of suspen- 

 sion of the testis on its inner border these tubes unite to form 

 an elaborate network of tubes placed on the inner face of the 

 testis an arrangement very similar to that often found in Elas- 

 mobranchii (vide F. M. Balfour, Monograph on the Development of 

 Elasmobranch Fislies, plate 20, figs. 4 and 8). 



We have figured this network on the posterior lobe of the 

 testis (fig. 58 B), and have represented a- section through it 

 (fig. 59 A, n.v.e.), and through one of the vasa efferentia (v.e.) 

 in the mesorchium. Such a section conclusively demonstrates 

 the real nature of these passages : they are filled with sperm 

 like that in the body of the testis, and are, as may be seen 

 from the section figured, continuous with the seminal tubes of the 

 testis itself. 



At the attached base of the mesorchium the vasa efferentia 

 unite into a longitudinal canal, placed on the inner side of the 

 kidney duct (Plate 39, fig. 58 A, I.e., also shewn in section in 

 Plate 39, fig. 59 B, I.e.). From this canal tubules pass off which 

 are continuous with the tubuli uriniferi, as may be seen from 

 fig. 59 B, but the exact course of these tubuli through the kidney 

 could not be made out in the preparations we were able to 

 make of the badly conserved kidney. Hyrtl describes the 

 arrangement of the vascular trunks in the mesorchium in the 

 following way (No. 11, p. 6): "The mesorchium contains vas- 

 cular trunks, viz., veins, which through their numerous anasto- 



1 The females we examined, which were no doubt procured at the same time as 

 the male, had their oviducts filled with ova : and it is therefore not surprising that 

 the vasa efferentia should be naturally injected with sperm. 



