286 



In these each eye is composed of many cells crowded into a 

 spheroidal mass still connected with the cuticle in many cases. 



The pigmented portions of these cells form a deep optic or retinal 

 cup from the open pupil of which the lens mass may project towards 

 the cuticle. 



The retinal cup is lined by a layer of clear rods, each a part of 

 one retinal cell. 



Between these rods and the part of the lens occupying the pupil 

 there may be interposed a »vitreous body« or the lens itself may fill 

 all the central space within the layer of rods. 



The lens and the vitreous body may present indications of being 

 composed of elements regarded as prolongations of the rods and thus 

 of the retinal cells. 



The lens is frequently connected with the cuticle by a slender 

 stalk. When the cuticle is invaginated this concerns only this stalk 

 and not the whole eye. 



The retina is to be regarded as a single layer of epidermal cells 

 each of which has elongated in such a way that its nucleus in the 

 pigmented part has receded from the cuticle Avhile its clear, cuticular 

 end has fused more or less with that of the other cells to form the 

 layer of rods, the lens and the vitreous body when present. 



Cases in which the eyes are hurried within the brain are to be 

 regarded as secondary and either degeneration or in addition partly 

 retentions of larval conditions. 



A few most complex eyes may prove to have closed retinal vesi- 

 cles, secondarily removed from the epidermis. 



The forming eyes show no sign of invagination , but strengthen 

 the above conceptions. 



Baltimore, May 25 1891. 



2. Zur Embryologie der Insecten. 



Von V. Grab er in Czemowitz. 



eingeg. 12. Juni 1891. 



1 . Meloë scah'iusculus Brdt. 

 Primäre Segmentierung. Bei M. proscarabaeus läßt J. Nus- 

 baum 1 zuerst — an der Gastral- oder Ptychoblastrinne — eine mi- 

 krosomitische, dann — nach erfolgtem Schluß des Blastoporus — eine 



1 J. Nußbaum, Przyczynek do embryologii Maika. Lemberg. Kosmos 1891. 

 (Das erste diese Arbeit enthaltende Heft wurde bereits im Sommer des Vorjahres 

 ausgegeben.) 



