Basic Structure of Vertebrates 



PROTONEPHRIDIUM 



PRONEPHROS 



MESONEPHROS 



CHORDATE KIDNEYS 



Fig. 77. A diagram illustrating the four types of kidneys which occur in chor- 

 dates. The excretory tubules in Amphioxus are ectodermal in origin like the proto- 

 nephridia of annelids, while they are mesodermal in vertebrates. In the course of 

 phylogenesis the excretory organs of chordates have been successively pronephros, 

 mesonephros, and metanephros. (Courtesy, Neal and Rand: "Chordate Anatomy," 

 Philadelphia, The Blakiston Company.) 







Fig. 78. Diagrams of urinogenital structures in (A) indifferent and female 

 elasmobranchs and amphibians; (B) male elasmobranchs and amphibians; (C) male 

 amniote (mammal); (D) female amniote (mammal), (ft) Urinary bladder; (c) cloaca; 

 (e) epididymis; (/) Fallopian tube; (g) gonad; (h) "stalked hydatid"; (k) kidney 

 (metanephros); (/) longitudinal tubule: (m) Miillerian duct (oviduct), rudimentary 

 in B and C; (mn) mesonephros; (o) ovary; (ot) ostium tubae abdominale; (pd) para- 

 didymis; (po) paroophoron; (pv) parovarium; (r) rectum; (/) testis; (u) uterus; 

 ((if;) urethra; (ur) ureter; (va) vas aberrans; (vd) vas (ductus) deferens; (ve) vasa 

 ell'erentia; (w) Wolffian duct, urinary in t, urinogenital in B, genital in C, and 

 rudimentary in D. (Courtesy, Kingsley: "Comparative Anatomy of Vertebrates," 

 Philadelphia, The Blakiston Company.} 



