OFTB* 



UNIVERSITY 



DICHOTOMY. 



attached only by the pelvis may result, every part of 

 the body and limbs being reduplicated, as in the case of 

 the Two-headed Nightingale. 



Such specimens occur throughout the vertebrate sub- 

 kingdoms. Two embryo sharks 

 are shown in fig. 66. They are 

 united in the ventral aspect in 

 the caudal region ; the remains 

 of a single yolk sac exists 

 between the pectoral fins, and 

 serves as additional evidence to 

 indicate their origin from a 

 single yolk. These sharks, with 

 some similar specimens, are pre- 

 served in the museum of the 

 Royal College of Surgeons. The 

 catalogue states that " a female 

 shark was taken in the Indian 

 Ocean. When brought on deck 

 and cut up, about thirty young 

 escaped from the abdomen. The 

 specimen lived for two days in a 

 bucket of sea-water. Several 

 examples of sharks, trout, 

 mackerel, and salmon redupli- 

 cated in this manner have been 

 recorded. Rauber has contri- 

 buted some excellent observations on this subject. He 

 has been successful in detecting many cases of duplicity 

 of the medullary folds, and the evidence seems to indicate 

 that, had they continued to develop, double embryos 

 would have resulted. 



FIG. 66. Two embryo Sharks 

 joined ventrally. 



