J28 



EMBRYOLOGY. 



they are composed become longer and more tortuous ; they 

 evidently secrete, and with their elongated common ducts, to 



which they look as if they 

 were attached, terminate in 

 the cloaca ; betwixt their 

 component shut sacs num- 

 bers of small points, which 

 consist of little convoluted 

 hanks of vessels, in every 

 particular like the Malpi- 

 ghian bodies of the kidney, 



mav be observed. The kid- 



it 



neys show themselves be- 

 hind and above the Wolffi- 

 an bodies on either side of 

 the spinal column ; at first 

 they are lobulated greyish 

 masses, which sprout by 

 the outer edges of the 

 Wolffian bodies; this is 

 plainly to be seen on the 

 sixth day, perhaps even 

 sooner ; the ureters are 

 formed afterwards as their 

 especial excretory ducts. 

 The kidneys arise as inde- 



Fig. 352. Cluck with part of the 

 yolk, a, a, which communicates, hy 

 means of the delicate vitello-intestinal 

 duct, with the noose of the jejunum i, 

 which at this time lies within the 

 funis umbilicalis ; c, c, vasa lutea. B, 

 separate views of the anterior extremity, 

 which shows a distinct division into 



three digits, a, and of the posterior ex- pendent formations ; and, 

 tremity, which shows traces of four independently of them, the 



capsulse supra-renales are 



evolved on their upper or anterior edge. The reproductive 

 organs, which had appeared as little marginal lappets, now 

 form two longish-shaped white bodies, and lie behind the 

 supra-renal capsules, at some little distance from these, on the 

 inner edge of the Wolffian body ; they are still of like size, 

 and it is impossible to distinguish whether testicles or ovaria 

 will be produced; so that of all the principal organs the ge- 

 nital are those thM are the latest recognizable in their rudi- 



v_^ 



ments, and distinguishable in their future special forms. 

 The vessels of the allantois are developed with great vigour ; 

 two arteries arise from the aorta, and a large vein runs on 

 the under edge of the liver to the vena cav^, along with the 



