DICHOTOMY. 12 
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 
Boa 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 ina 
bucket of sea-water. Several 
examples of sharks, trout, 
mackerel, and salmon _ redupli- 
cated in this manner have been Fic. 66.—Two embryo Sharks 
recorded. Rauber has contri- ea ho 
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. 
\ ee 
