1897.] EYES OP THE OUDEB. PRIMATES. 185 



most books which treat on the subject we find it stated that 

 among mammals Man and the Anthropoid Apes (the Simiidse) alone 

 possess a macula ; but I find, as I will presently explain, that the 

 existence of the macula is not restricted to these only. 



In addition to the scarlet and lake-red branches of the retinal 

 vessels which proceed from the disc, a large number of interrupted 

 orange-yellow and red vessels, uniformly coloured and much 

 broader than the artery and the veins, can be observed, anasto- 

 mosing so as to form a network (see cc, Plate V.). These vessels 

 belong to the choroid, a vascular structure underlying the retina. 

 As that portion of the retina which lies in contact with the choroid 

 is pigmented, these choroidal vessels can only be distinctly observed 

 in fair people and in albinos. I am, of course, speaking of the 

 normal eye of the adult, and not taking into consideration de- 

 fective senile or pathological conditions. 



It is not only with regard to the degree of distinctness with 

 which the choroidal vessels can be observed that the ophthal- 

 moscopic appearance differs in fair and dark people. The colour 

 of the fundus likewise varies in proportion to the pigmentation of 

 the individual. In very fair people the colour is a bright vermilion, 

 which gradually tends towards a^ reddish brown in people with 

 very dark hair and sldn, until we find it of a chocolate colour in 

 the negro. Except in colour, the appearance of the fundus oculi 

 does not differ in the various races of Man. I need hardly say 

 that of course the colour of the macula varies with the general 

 colour of the fundus, being always distinguishable as a darker 

 patch than the rest, although occasionally, in Aery dark Europeans, 

 I have seen it of a decidedly redder hue than the rest of the 

 fundus. 



The chocolate-coloured field, with a darker chocolate-coloured 

 circular patch indicative of the macula region bordered by a 

 bright scintillating ring, characteristic of the negro, is likewise 

 what we find when we examine the eye of the Simiidae, but we 

 find the fundus varies greatly in colour once we descend below this 

 group. Even in the Gibbons, the lowest of the Simiidae, we 

 already find a commencement of this departure. 



Throughout the Anthropoids the arrangement of the retinal 

 vessels is the same as in Man, the first indication of variation 

 being found as soon as we reach the Lemuroidse. 



The disc is oval, with the long axis vertical, at times more or 

 less circular, or practically the same as in Man. Here again we 

 only find a difference in the Lemuroidse, which all have a circular 

 disc. 



The Lemuroidse have no macula, the existence of which ceases 

 with the last of the true Monkeys. In other words, we find a 

 striking resemblance between the appearance of the eye of Man 

 and the entire order Anthropoidse, although in many details we 

 can trace as we descend the scale a tendency towards that lower 

 form which reveals itself to us when we examine the Lemuroidse ; 

 and here again we find a gradual departure from the higher type 



