6o KINGSLEY. [Vol. I. 



by the proximal ends of the retinophorae, as maintained by 

 Patten. 



Carriere ('<?(5) led by Locy's observations, publishes some 

 results of studies on the eyes of Chrysides and Ichneumoids, 

 which, in the absence of illustrations, are absolutely unin- 

 telligible. The hypodermis cells elongate, and then divide 

 into two layers, and at the edge of this patch a pouch-like 

 invagination begins, going obliquely downward, and carrying 

 with it both layers in their " normalan Lage." Here arises the 

 difficulty; how many layers result? The outer layer is 

 described as the lens-building — the inner, as the potential retina 

 forming; but which "inner" and which "outer" layer is 

 referred to of the six which may exist is left in doubt. Next, 

 some of the invaginated cells are represented as extending to 

 the surface and sharing with the superficial cells in the forma- 

 tion of the lens. In the meantime the retinal cells have 

 separated from the hypodermis, and form the pigment and rods, 

 while the lens-forming cells have never severed their connection 

 with that layer. Further, the invaginated pouch is never sepa- 

 rated from its parent layer. 



The last author to be mentioned on the development is Dr. 

 Reichenbach, who has given us by far the most complete account 

 of the development of a compound eye which has yet appeared. 

 He describes {^86, pp. 85-96) the development of the eye of 

 Astacus, and, in the earlier stages, there is a striking similarity 

 in our results, when one bears in mind the considerable difference 

 in the size of the eggs investigated. One difference is, how- 

 ever, to be noticed : I could not see the cell-divisions so plainly 

 shown on the beautiful plates of the Frankfurt naturalist ; and, 

 besides, gastrulation takes place in Crangon before, not after, the 

 formation of the optic lobes. Beyond this we agree perfectly in 

 the position and direction of the optic invagination ; but in 

 Astacus the invagination is solid. This portion is represented 

 as becoming separated from the parent layer and coming to lie 

 beneath a patch of epiblast in front and a little outside the place 

 of invagination. This patch, interpreted as the rudiment of the 

 crystalline-cone layer, soon thickens, and becomes several layers 

 of cells or nuclei deep, while the invaginated portion folds so as 

 to inclose a cavity with an inner and outer wall. Here come 

 our differences, which naturally affect all the subsequent stages- 



