186 DR. G. LINDSAY JOUXSON' ON THE [Jan. 19, 



as we wend our way from the Lemurs through the Galagos down 

 to the Aje-J\ye. 



The eyes of all the Primates below Man are smaller than our 

 own, but this is not so in proportion to the size of the body. 

 I have found, for instance, that the transverse diameter of the 

 globe of the eye of the half-grown Gorilla which lately died in the 

 Society's Gardens measured 207 mm., which is the size of the 

 eye of a child between the age of 9 and 11. Of course the eye of 

 a small Marmoset is very much smaller, being in proportion to the 

 size of the animal. 



There are other distinctive differences between Man, the 

 Monkeys, and Marmosets, in other words between the Anthro- 

 poids on the one hand and the Lemuroidse on the other. 



The pupil of Man and the Anthropoids is ahvays circular, 

 whilst we find a vertically oval pupil in all the Lemuroidie. In 

 addition to this I find from repeated observations that all the 

 Anthropoids or true Monkeys are able to accommodate their eyes 

 for near objects by converging both eyes on to a single point, 

 and in so doing the pupil contracts as in Man, though to a less 

 degree. The Lemuroidse have not this power of convergence ; and 

 although I have noticed the power of convergence in all the 

 Monkeys, I find it is only a transition stage — that is to say, they 

 employ it with hesitation and difficulty, much in the same way as 

 an infant uses its legs when learning to walk, since they cannot 

 converge for more than one or two seconds at most. If you hold 

 a small bright-coloured object near the nose of a Monkey, you will 

 observe the eyes converge immediately in a horizontal plane, and 

 the pupils contract slightly, but the next moment the eyes return 

 to parallel vision, though not necessarily in a horizontal plane, being 

 often accompanied by a slight elevation upwards. 



We thus find that we must draw a broad distinction between 

 Man and Monkeys as a group and the Lemuroids. Man and 

 all the Monkeys and Marmosets without exceptioia possess a 

 macula, a circular pupil, and converge when accommodating for 

 near objects. These characteristics are necessary for binocular 

 vision. The Lemuroidse have not got binocular vision and therefore 

 we find aU these peculiarities absent. 



Going more into detail we find that every family has some 

 characteristic peculiarity. Thus the eyes of the Gorilla, Chimpanzee, 

 and the Oraug closely resemble that of the negro, except that 

 around the disc the whitish fine streaks are more marked. Were 

 they as strongly marked in Man they would be attributed to a con- 

 genital defect know-n as opaque nerve-fibres, although the defective 

 human eye shows these opaque nerve-fibres wholly opaque, whilst 

 in these Apes they are more or less translucent. These translucent 

 nerve-fibres radiating from the disc become someu hat more marked 

 as we descend the scale. In the Gibbon we find an extreme 

 prominence of the choroidal vessels. 



In the next family, the Cercopithecids, we notice in some 

 genera an approximation to the Simiids, notably in the Black Ape, 



