520 DEVELOPMENT OF ELASMOBRANCH FISHES. 



The section illustrates (i) the formation of a Malpighian body (mg) from the 

 dilatation at the end of a segmental tube, (i) the appearance of the rudiment of the 

 Miillerian duct in the male (od'). 



Figs. 7 a, 7 b. Two longitudinal and vertical sections through part of the kidney 

 of an embryo between stages L and M. Zeiss B, ocul. 2. 



7 a illustrates the parts of a single segment of the Wolffian body at this stage, vide 

 p. 491. The segmental tube and opening are not in the plane of the section, but the 

 dilated vesicle is shewn into which the segmental tube opens. 



7 b is taken from the region of the kidney proper. To the right is seen the opening 

 of a segmental tube into the body-cavity, and in the segment to the left the commenc- 

 ing formation of a ureter, vide p. 502. 



Fig. 8. Longitudinal and vertical section through the posterior part of the kidney 

 proper of an embryo of Scyllium canicula at a stage between N and O. Zeiss A, 

 ocul. 2. 



The section shews the nearly completed ureters, developing Malpighian bodies, &c. 



Fig. 9. Longitudinal and vertical section through the anterior part of the kidney 

 proper of the same embryo as fig. 8. Zeiss A, ocul. 2. 



The figure illustrates the mode of growth of the developing ureters. 

 9 A. More highly magnified portion of the same section as fig. 9. 

 Compare with transverse section fig. 4. 



Fig. 10. Longitudinal and vertical section through part of the Wolffian body of 

 an embryo of Scyllium canicula at a stage between O and P. 



The section contains two examples of the budding out of the vesicle of a segmental 

 tube to form a Malpighian body in its own segment and to unite with the tubulus of 

 the preceding segment close to its opening into the Wolfnan duct. 



