342 Miscellaneous Intelligence. 
stances of which the body is composed have so large an ampli- 
tude of vibration that the bond which unites them can no longer 
bring them again into their former positions. The otential of 
the substances is again raised by a quantity which is proportional 
to its chemical a ae Again, we may increase the amplitude 
f vibration, i. temperature of the molecules, and imagine 
the possibility of iaakee un and higher degrees of dissociation.” 
sor | apa remarks as follows on the development of 
organs of v 
** Another "important fact shown by embryology is that the 
oentral nervous system, and percipient portion of the organs of 
special sane, are often Dae rom the same part of the primitive 
5 papain Thus, in ourselves and in other vertebrate animals 
So uahies part of the eye, known as the retina, is formed from 
wo lateral lobes of the front part of the primitive brain. The 
— erystalline lens and cornea of the eye are, however, subsequently 
formed from the skin. 
The same is true for the peculiar compound eyes of crabs or 
Crustacea. The most important part of the central nervous sys- 
tem of these animals is the pide gl grape ganglia, often known 
as the brain, and these are formed in the embryo 0 from two a 
ened patches of the skin at the ont a of the The 
thickened patches become gradually detached from ce oe 
remaining covered over by a layer of skin. They then constitute 
the supracesophageal ganglia; but they form not only the ganglia, 
but also the rhabdons or retinal elements a oe eye—the parts in 
fact which correspond to the rods and cones our own retina. 
The layer of epidermis or skin which lies Pics iiaéely above the 
