60 BULLETIN OF THE 



those of Lankester and Bourne, and although he has given no definite 

 description of a sclera-matrix in these eyes, yet one may fairly infer 

 (cf. I. c, p. 77) his belief in such a matrix, and can find in his figure 

 (left side) indications of nuclear structures which easily admit of such an 

 interpretation. These (sclera-matrix 1) cells I consider to be, in any 

 event, the equivalent of what Lankester and Bourne have described as 

 " interneural epithelial cells," the nature of which, it will be observed 

 from their figures (Figs. 2, 3) and descriptions, differs considerably in 

 Euscorpius and Androctonus. 



But in addition to the considerations presented by Lankester and 

 Bourne, there is another objection to the interpretation here proposed, 

 Avhich at present I am not able to explain. The direct and apparently 

 primitive manner in which the retinal cells are continued into the nerve 

 fibres seems to point to a normal rather than an inverted condition of 

 the retina. 



In either event, tlie nature of the lateral eyes in scorpions is deserving 

 of further study ; and it will not be surprising if it is found that they 

 arise by a process of infolding accompanied by inversion of the retina. 



Grenacher ('78) has given a figure of an ocellus in one of the Phalan- 

 gidce which indicates the presence of a distinct layer of cells (" vitreous") 

 in front of the retina ; and although he has not seen anything of a layer 

 behind the retina, these eyes present no more serious obstacle to an origin 

 by involution than do most of the hitherto published figures of the eyes 

 of spiders. 



The conditions in the eyes of Myriapoda leave more room for doubt. 

 Graber, Grenacher, and Sograff are the only authors who have recently 

 given them any considerable attention. 



The eyes in Myriapods — aside from Scutigera, in which they are of 

 a conspicuously different type — are apparently either monostichous 

 (Chilognatha) or so-called diplostichous (Chilopoda). The latter evi- 

 dently approach more nearly the conditions found in Arachnoidea, and 

 will be considered first. 



Graber ('79, p. 59) claimed their substantial agreement with the ocelli 

 of the Arachnoids and Hexapods. While Greiiacher's subsequent work 

 has made much of Graber's description appear illusory, there are still 

 sonm points in which it is probable that Graber has given reliable presen- 

 tations of the histological structure. There is, at least, one thing in 

 which T believe his observations deserving of more attention than they 



