434 Miscellaneous. 



through the whole winter ; for if each female furnishes only one egg 

 there are an immense number of females. The egg hatched on the 

 11th May [March?]; and I placed the little Aphis which issued 

 from it, and which is, of course, the larva of the foundress-form, 

 upon a small poplar, which I planted on purpose in my garden. 

 Now, on the 3rd April, I have the satisfaction of seeing my little 

 artisans at work, burying themselves in the tender stalks of the 

 first buds, and beginning to disappear beneath a little elevation 

 which surrounds them like a halo, of a bright carmine tinge. 



I had wished to be able to give the complete history of the bio- 

 logical cycle of this Aphis ; but I hope that what I have seen may 

 facilitate the study of these interesting metamorphoses by other 

 observers. However, the theories which I have already had the 

 honour of presenting to the Academy with regard to Phylloxera and 

 other species of Pemphigians are here again fully confirmed : there 

 are four larval forms preceding the sexual forms ; and of these four 

 forms two are apterous and two winged. — Comptes Renclus, April 5, 

 1880, p. 804. 



Structure of the Eye of Limulus. 

 By A. S. Packard, Jun. 



The eyes of the horseshoe or king crab are four in number, con- 

 sisting of a pair of compound eyes situated on the side of the head, 

 and a pair of small simple eyes on the front of the head. As 

 described by A. Milne-Edwards and Owen, the optic nerves to these 

 eyes are very long and slender. Those distributed to the larger 

 compound eyes are very long, and close to each eye subdivide into 

 an irregular plexus of fine nerves, a branch being, as we have 

 found, distributed to each facet composing the compound eye. The 

 structure of the eye is very unlike that of any other Arthropod eye. 

 The cornea is simply a smooth convex portion of the integument, 

 which is much thinner than the adjoining part of the chitinous 

 skin. There are no facets, the cornea externally being structure- 

 less, simply laminated like the rest of the integument. In the 

 internal side of the cornea are a series of solid chitinous conical 

 bodies, separated from one another by a slight interspace and in 

 form resembling so many minie-rifle balls ; the conical ends of 

 these solid cones project free into the interior of the body, and are 

 enveloped in a dense layer of black pigment. Within the base of 

 these cones are secondary, shallow, cup-like bodies or shallow 

 secondary cones. It is these primary cones which, seen through 

 the smooth, convex, translucent cornea, give the appearance of a 

 faceted surface to the external eye. 



All the parts thus far described, except the pigment layer, are 

 moulted with the rest of the crust ; and the large, long, slender 

 cones can be easily seen by viewing a piece of the cast-off eye, the 

 solid cones being seen projecting from the inner surface of the 

 cast-off cornea. 



The internal structure of the eye is very simple. There are no 

 cones and no rods ; but a branch of the optic nerve impinges directly 



