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LABORATORY MANUAL FOR VERTEBRATE ANATOMY 



functional cases. The glomeruli of the pronephros are generally of the type known as exter 

 glomeruli, that is, they project into the coelom adjacent to the nephrostome and are not direc 

 associated with the tubule (Fig. 61). In some cases, however, internal glomeruli which proj 

 into the tubule occur. 



Fig. 60. — Diagrams to show the development of the three kidneys and their ducts and t 

 relation to the male gonad. A, early stage showing the pronephros a developing from the anterior 

 of the mesomere c and the pronephric duct b which has not yet reached the cloaca e. B, next st; 

 illustrating the degeneration of the pronephros at /, the development of the mesonephros h from 

 middle portion of the mesomere, the junction of the pronephric duct, now the mesonephric due 

 with the cloaca and the beginning of the metanephric evagination i from the mesonephric duct. C, 1; 

 stage, showing connection between certain tubules of the mesonephros and the testis j by mean 

 tubules, the vasa efferentia p, which grow out from the mesonephros; and the penetration of the m 

 nephric evagination into the posterior end of the mesomere where it is subdividing to form the collec 

 apparatus I, which becomes associated with secretory metanephric tubules m, developed in the m 

 mere. D, final stage, in which the mesonephros has disappeared except for the remnant q which i 

 nects with the testis j by means of the vasa efferentia p; the mesonephric duct g persists as the 

 deferens; the two parts of the metanephros shown in C have united to form a single organ r. a, 

 nephros; 6, pronephric duct; c, mesomere or nephrotome; d, intestine; c, cloaca; /, degenera 

 pronephros; g, mesonephric or Wolffian duct ; h, mesonephros or Wolffian body; /, metanephric evag 

 tion from the Wolffian duct in B, ureter in C and D; j, testis; k, coiled portion of the vas deferens fc 

 ing part of the epididymis; /, collecting part of the metanephros derived from the Wolffian duct; 

 execretory tubules of the metanephros derived from the mesomere; n, nephrostome; o, renal corpr 

 or Malpighian body; p, vasa efferentia; q, remnant of the mesonephros, forming part of the epididy 

 r, metanephros. 



b) Mesonephros: The second vertebrate kidneys are the paired mesonephroi (singi 

 mesonephros), also known as the Wolffian bodies, after the embryologist Wolff, who 



