DUPLICITY. 13 



It is probable, however, that the axis was originally dichoto- 

 mous, but that development of one portion is arrested at an early 

 stage. Another hypothesis is that the second pelvis originates 

 in the process of repair consequent on an injury to the embryo. 

 Valentin injured the posterior extremity of an embryo and pro- 

 duced this condition. It is impossible with our present know- 

 ledge of the subject to decide on the merits of these two hypo- 

 theses. Without Valentin's experiment analogy would lead us 

 to adopt the former view unreservedly. The term dipygus has 

 been restricted in this Catalogue to such forms. 



65. The skeleton of a dipygous Kitten. 



The axis deviates to the right side, and the laminae of the ver- 

 tebrae are deficient in the lumbar region. The right innominate 

 bone of the right axis and the left innominate bone of the left axis 

 are united by the pubic symphysis ; each bears a perfect limb. The 

 other innominate bones are rudimentary, and their ilia and aceta- 

 bula are fused together. The tuberosities of the ischia of these 

 median imperfect bones are ankylosed with those of the more 

 developed fellow bones. The left femur of the right axis and the 

 right femur of the left axis are fused into a single broad bone with 

 two heads ; this articulates with a single median tibia and two 

 fibulae. There are two perfect feet to this median limb. 



66. A dipygous bitch Pup with the abdomen laid open to show 



the viscera. 



The innominate bones and additional posterior extremities are 

 precisely like those of No. 65. The rectum bifurcates about an 

 inch and a half from its extremity ; the right portion is blind. 

 The external sexual organs are double. There are two vaginae 

 and two bladders. The right bladder is smaller than the left. 

 The right kidney is very small ; its ureter becomes impervious about 

 a line from its inferior extremity, where it is connected with the 

 left vagina. The left kidney is very large ; its ureter opens into 

 the left bladder. A bristle points to the right kidney. The va- 

 ginae and anus are also marked with bristles. 



Hunterian. 



67. The external and internal generative organs and a portion 



of the double pelvis of a large Dog, dissected. 



There is no history of the preparation ; but it is probably from a 

 dipygous animal very similar to the last, except that the posterior 



