198 



ELEMENTS OF BIOLOGY 



FISH AND AMPHIBIA REPTILES AND BIRDS 



TESTIS 



KIDNEY 



MALE 



FEMALE 



MALE 



REPTILES AND BIRDS 



MAMMALS 



ovAify 



KIDNEY 



BLADDER 



CLOACA 



TESTIS 



OYIDUCT 



BLADDER 



PROSTATE 

 GLAND 



PENIS 



OVARY 



SPERM DUCT 



KIDNEY 



URETER - 



SEMINAL 

 VESICLE 



f-^ RECTUM 

 ^ '^URETHRA 



VESTIBULE 



OVIDUCT 



UTERUS 



VAGINA 

 BLADDER 



FEMALE 



MALE 



FEMALE 



Fig. 135. — Diagrams showing comparatively the homologous parts of the excretory 

 and reproductive organs of vertebrates. One side only is shown. It will be noted that 

 in the higher mammals the cloaca docs not exist in the adult; its place is taken 

 by urinary and reproductive canals and the posterior end of the digestive canal, the 

 rectum. (After Kiihn, slightly modified: Gnmdriss der allgemeinen Zoologie. Georg 

 Theime, Leipzig.) 



