NOTES. 3875 
lar; or, in other words, it is round in short-sighted animals, and flattish in 
the long-sighted. The lens of the Invertebrate is not exactly the same as 
the lens of the Vertebrate eye, though it performs the same function; it is 
really a part of the cornea. 
'o4 The Ant has 50 in each eye, the House-fly 8000, the Dragon-fly 12,500. 
205 The pigment, therefore, while apparently in front of the retina, is real- 
ly behind it, as in Vertebrates. The layer beneath the cornea, serving as an 
‘iris,’ is wanting in nocturnal insects, since they need every ray of light. 
The optic nerve alone is insensible to the strongest light. 
+06 Tt should be noticed that this corresponds with another peculiar fact 
already mentioned, that either hemisphere of the brain controls the muscles 
on the opposite side of the body. In Invertebrates the motor apparatus is 
governed on its own side. 
107 Sharks have eyelids, while Snakes have none. The third eyelid (called 
nictitating membrane) is rudimentary in Mammals. 
108 An infant would doubtless learn to walk if brought up by a wild beast, 
since it was made to walk. Just as an infusorium moves its cilia, not be- 
cause it has any object, but because it can move them. New-born puppies, 
deprived of brains, have suckled; and decapitated centipedes run rapidly. 
Such physical instincts exist without mind, and may be termed ‘blind im- 
pulses.” 
109 We say ‘“‘apparently,’”’ because it may be a fixed habit, first learned by 
experience, transmitted from generation to generation. A duckling may go 
to the water, and a hound may follow game in some sense, as Sir John Her- 
schel takes to astronomy, inheriting a taste from his father. Breeders take 
advantage of this power of inheritance. 
110 “Thus, while the human organism may be likened to a keyed instru- 
ment, from which any music it is capable of producing can be called forth 
at the will of the performer, we may compare a Bee, or any other Insect, 
to a barrel-organ, which plays with the greatest exactness a certain num- 
ber of tunes that are set upon it, but can do nothing else.’””—CARPENTER’S 
Mental Physiology, p. 61. This constancy may be largely due to the uni- 
formity of conditions under which Insects live. 
111 We may say, as a rule, that the proportion of instinct and intelligence 
in an animal corresponds to the relative development of the spinal cord and 
cerebrum. As a rule, also, the addition of the power to reason comes in 
with the addition of a cerebrum, and is proportioned to its development. 
Between the lowest Vertebrate and Man, therefore, we observe successive 
types of intelligence. Intelligence, however, is not according to the size of 
the brain (else Whales and Elephants would be wisest), but rather to the 
amount of gray matter in it. A honey-comb and an Oriole’s nest are con- 
structed with more care and art than the hut of the savage. It is true, this 
is no test of the capability of the animal in any other direction; but when 
they are fashioned to suit circumstances, there is proof of intelligence in 
one direction. Physiologists now hold that the cerebrum is not essential to 
consciousness. 
12 Air-breathing Vertebrates, as the Manatee and Sea-lion, are exceptions. 
There are, doubtless, many sounds we can not hear. The noise of a Spider 
