DICHOTOMY. 119 
spring of 1879 he had in an aquarium two or three 
thousand eggs of Amblystoma punctatum for the purpose 
of studying their development. One day he chanced to 
find one with the medullary folds nearly completed, but 
they had not united at the cephalic end, and appeared to 
be much rounded at their anterior ends, instead of having 
the ordinary vague outlines; he kept it apart, therefore, 
a 
Fic, 65.—A two-headed Foal ; anterior dichotomy. 
and watched it. Each free portion of the medullary fold 
developed a perfect head, which, at first partly united, 
became gradually more so, until they were connected 
throughout their entire length. Posterior to the heads 
there was no sign of duplicity. 
In this case a two-headed monster, with a regular 
symmetrical body, was developed from one egg, and 
