HAMLYN'S MENAGERIE MAGAZINE. 
was different from the gorilla. He was playful 
even when he got old. That was a fact they had 
never quite appreciated, and the change in this 
respect was as great in anthropoids as in the 
human race. 
Another picture of a chimpanzee showed a 
different type of animal. Some people thought 
it was a gorilla, but the lines under the 
nose and the ears distinguished it. While the 
chimpanzee and the gorilla were different animals, 
the differences were not great and the degree of 
difference between them represented an interest- 
ing study in evolution. Was it not possi- 
ble that the chimpanzee might be trans- 
formed into the human type? The lecturer pointed 
to the forearm of an adult chimpanzee and indi- 
cated all that was left of the tendon leading to 
the thumb, pointing out that it was impossible for 
such an animal to regain the flexibility of the 
thumb. Therefore it was impossible for an animal 
like that to gain the human condition. That fact 
was not new; it was known to Huxley. Describing 
some of the characteristics of the gorilla and the 
chimpanzee, the lecturer drew a parallel between 
the extinct Neanderthal man and the chimpanzee. 
The next diagram showed differences in 
the size of the brain. As far as size was con- 
cerned they could not draw a sharp line between 
the gorilla and the chimpanzee. They knew the 
brain of Neanderthal man was very big. The 
gorilla brain was bigger than the chimpanzee. 
The arm centres of the brain were big, and the 
centres for the lower extremities showed an equal 
degree of differentiation. The mapping out of 
the cortex would make it possible to compare the 
human and anthropoid brains with a greater 
degree of precision. There was a close resem- 
blance in the motor areas of the gorilla and the 
chimpanzee, but there was slight differences in 
detail. Point for point the two animals were 
almost alike, and yet he thought in nine times out 
of ten he could tell a gorilla brain from that of a 
chimpanzee. Nature had not yet got those two 
forms clearly separately from each other. The 
Island of Reil was completely cut off in the 
gorilla's brain. 
The lecturer proceeded to show the differences 
in the lower jaws of the gorilla and the chimpan- 
zee. The difference in mass was enormous. The 
gorilla, had enormous muscular power and the 
chimpanzee small. The chief difference was in 
the teeth. The difference between the gorilla 
and the chimpanzee in the matter of teeth was 
simply enormous. They had difficulties in the 
matter of distinguishing brains, but in the teeth 
there was no difficulty. With the Neanderthal 
man it was the same; they could tell him by his 
teeth. So they could the o-orilla. He did not sav 
there was any direct relationship, but he was 
directing attention to the physiological resem- 
blance. There were the same differences between 
the modern man and the Neanderthal man as 
between the gorilla and the chimpanzee. 
Pictures of various palates indicated enor- 
mous difference between the chimpanzee palate 
and that of the gorilla. The human palate was 
the same width, but much shorter. Dealing with 
the powers of mastication, the lecturer pointed 
out that the canine teeth are long in the gorilla. 
In the chimpanzee they were not so> long. The lec- 
turer drew attention to the difference in the shape 
of the teeth and of their cusps. In the gorilla they 
were prismatic; in the chimpanzee rounded with 
a tendency to go out in a feathery pattern. In 
the human type the cusps were rounded. 
The lecturer produced the skull of a boy. One 
side of the face had grown at a great 
rate, the muscles of mastication on the same 
side were over-grown. The other side had 
grown at the normal rate. The teeth in the adnor- 
mal side had outgrown the normal side. The 
teeth were formed three months before birth. 
Here was Nature doing an experiment. She was 
producing gorilla teeth on one side and the teeth 
of the chimpanzee on the other. If we knew how 
that was done we should have a solution of the 
problem between the gorilla teeth and the chim- 
panzee. Biologists had a great deal to learn from 
those experiments. They had no idea how the 
differences on the two sides in the boy's skull 
were produced. 
A diagram of a baby gorilla skull inside an 
adult skull was shown to illustrate the great trans- 
formation that took place during growth. These 
changes were all correlated with mastication, and 
they took place between the third and the thir- 
teenth year. The gorilla's skull had a great crest; 
the chimpanzee had not. In the chimpanzee the 
muscle of mastication stopped short of forming 
a great crest like that on a fireman's helmet. 
The point that interested the lecturer was that 
the chimpanzee represented an arrested stage in 
the gorilla. It gave a clue as to how evolution 
might work. He did not think the difference 
between the skull of that gorilla and that chim- 
panzee was essentially greater than between the 
Neanderthal man and modern man. 
Dealing with the growth of the face, the 
lecturer pointed out that the gorilla's face was 
longer than the chimpanzee's. Man had a shorter 
face than the chimpanzee. The greatest differ- 
ence between the chimpanzee and the gorilla lav 
in the apparatus of mastication, the size of the 
muscles of mastication, and the teeth. Smaller 
points were very difficult to define. In the skull 
of the chimpanzee the nasal bones were small. In 
the gorilla they were wide and went below the 
margin of the orbit. There was the same differ- 
ence between Neanderthal man and modern man. 
(To be continued.) 
