i 4 4 THE HUMAN SPECIES 



uterus opening into a single vagina, as found in many of the 

 rodents, and in the partially divided uteri of other mammals, 

 occurring also not infrequently in the human subject. 



With regard to the copulative organs, animals as low down 

 in the scale as the worms possess a penis, to which corresponds 

 in the female a vagina with bursa copulatrix for the admis- 

 sion of the penis. In the Crustaceans (Arthropoda) a canal in 

 the sexual organ (in the form of a foot) serves as penis for the 

 introduction of semen ; in the Insecta the male is furnished 

 with a copulative organ, varying in form, which is introduced 

 into the bursa copulatrix of the female. Of the Mollusca only 

 the Gastropoda and Cephalopoda possess a male copulative 

 organ ; among the latter one of the arms undergoes a curious 

 metamorphosis in order to serve as such. We find a similar 

 transformation of an organ in the fishes (Selache and Chimaera) 

 where a part of the ventral fin acts as spermatic duct and 

 sexual organ. Other of the Selache have a protrusile organ, 

 sometimes cartilaginous, similar to that of the Crustaceans, to 

 which corresponds in the female roach a smaller organ resem- 

 bling a clitoris. Surbeck considers the sexual organ of the 

 Cottus gobio, a sub-species of the Teleostes, to possess the 

 character of a penis, but Hyrtl points out that in the absence 

 of corpora cavernosa this structure in the Teleostes cannot 

 be regarded as a penis. 



Of the amphibians the salamanders possess a papilla open- 

 ing into the cloaca, while the reptiles have sexual organs either 

 proceeding from the wall of the cloaca in the form of tubes, or 

 constructed of fibrous tissue. 



In the saurians and snakes the protrusile tubes, furnished 

 with a spiral, seminal sinus, are dilated in the middle and 

 bifurcated at the extremity, the glans penis being provided with 

 spinous epithelium, which, however, is absent in the homologous 

 female gland, the clitoris. Both here, and in the tortoise and 

 crocodile, the higher vertebrate form of corpora cavernosa 

 cannot be said to be present. 



The copulatory organ of the birds bears a close resemblance 

 to that of the reptiles, being usually in the form of a tube sup- 

 ported by fibrous tissue ; the didactylous ostrich possesses a penis 

 consisting of two bodies united together and enclosed with a 



