No. 1.] ORIGIN OF HUMAN MONSTERS. 225 
the spinal canal being filled up with mesodermal tissue rich 
in blood-vessels. Where the cord is missing most of the 
spinal nerves appear to remain, and many dorsal ganglia can 
be made out. This all indicates that the changes in the cen- 
tral nervous system took place after the spinal nerves were 
developed from it. 
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Fic, 201b—Diagrammatic reconstruction of the embryo, showing the 
extent of the central nervous system. 5 times. 
The two eyes are united into a single one with a double 
retina, two lenses, a single choroid, and a single optic nerve; 
back of this it is double again. It certainly appears as if the 
two eyes have wandered together and have united in the 
middle line. 
The epidermis is quite complete, being broken through at 
the back of the head. The extensive ulcer which is found 
