MARMOSETS 47

simply the desire to achieve an object for the sake of
achieving an object, and he never rests nor allows his
attention to be distracted until it is done. This
monkey also found out how to open boxes with keys,
and did other noteworthy things. His rapidity of
discernment was very striking. When he went back
to the Zoological Gardens he always instantly re-
cognised the friends among whom he had spent his
holiday. ‘I purposely, says the doctor, ‘visited the
monkey-house on Easter Monday, in order to see
whether he would pick me out of the solid mass of
people who fill the place on that day. Although I
could only obtain a place three or four rows back
from the cage, and although I made no sound where-
with to attract his attention, he saw me almost im-
mediately, and with a sudden intelligent look of
recognition ran across the cage to greet me. When
I went away he followed me, as he always did,
to the extreme end of his cage, and stood there
watching my departure as long as I remained in
sight,’

The last and the smallest of the man-like animals
are the Hapalide or marmosets. Unlike the other
American monkeys, these have the same number of
teeth as man, although the arrangement is different,
there being three premolars and two molars, instead
of two premolars and three molars. Like all the rest
of the order, they have two incisors and one canine.
Of course we have taken it as generally known that
the dental formula of man is 2, 1, 2, 3, the first three
figures, the important ones, being easily rememberable
as giving the boiling-point of water. The tail of the