Eyes of Molluscs and Arthropods. 645 



Branchipus and Orchestia. 



I have Lad the pleasure of examining some well preserved 

 eyes of Branchipus Gruhii, prepared duriug my stay iu Leipzig-. The 

 four nuclei of the retinophorae are located at the outer euds of the cells, 

 over which they form a kiud of cap . situated in a thickening similar 

 to that fouud iu a corresponding positiou in the eye oi Petiaeus. The 

 corneal hypodermis is well developed and consists of a layer of inde- 

 finitely arranged cells upoii the inner surface of the unfaceted cornea. 

 The style of the retinophorae forms a spindle-shaped tube, largest near 

 the outer ends of the retinulae, and decreasing in diameter towards 

 either extremity ; the outer end hecomes directly continuous with the 

 calyx , while the slender inner one rests upon the basal membrane. 

 The tube, witb.in which may be seen the axial nerve fibre, is laterally 

 flattened , the two narrow walls being much thicker than the broad 

 ones. The cross nerve fibres within the calyx, together with the super- 

 ficial ones upon the walls of the same, may be seen bere just the same 

 as in Galathea^ Penaeus etc. from which they do not diflfer to any notice- 

 able extent. The four lateral thickenings seen in the calyx of Galathea. 

 and the outer row of pigmented cover cells (and of course the bacilli , 

 or their stalk-like ends) , are absent in Branchipus. 



In Orchestia , I have also seen in macerated specimens the same 

 nervous network upon the surface of the calyx, although I was unable to 

 detect cross Striae in the crystalline cones. Along the wall of the calyx, 

 which is almost completely filled by the crystalline cone, may be de- 

 tected severa! comparatively large , longitudinal fibres , from which a 

 great number of irregulär, smaller branches arise. 



A valuable confirmation of my opinion , that the corneal hypoder- 

 mis is the very much modified and reduced layer of similarly named 

 cells in the eyes of Myriapods and Spiders , was found on examining 

 some sections of embryo lobsters which were just ready to escape from 

 the chorion. Here the cells formed a broad and very distinct layer, 

 separated from the underlying ommatidia by an extremely delicate 

 membrane. An exactly similar condition was found in the eyes of larvai 

 Penaeus, or an allied genus. In both cases, the development of the 

 larvai cuticular hypodermis was much greater than in the adult, where 

 it is reduced to an almost unrecognizable thinness. Moreover, the nuclei 

 of these cells stain more deeply, and consequently are more easily re- 



