ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 425 



first sight, considerably from those of the female ; they belong, how- 

 ever, to the same type of aconic eye, and only present a different 

 stage in development. 



2. Aconic and pseudoconic eyes of insects. — The author does not 

 agree with Dr. Hickson in thinking that the difference between 

 pseudoconic and euconic eyes is slight ; on the other hand, he finds 

 that the refractive parts of the aconic and pseudoconic eyes are only 

 extreme forms of one type. The euconic eye is characterized by its 

 vitrellae passing at their free end into a common conical lens, while 

 the other forms a part of the crystalline cone. In the aconic type 

 the distal end of the vitrella becomes merely cuticularized, and the 

 simplest form is that in which the cornea simply forms a watch- 

 glass-like investment for the distal end of the vitrella ; there may be 

 further stages of complication, and the inner part of the corneal lens 

 often breaks up into two dissimilar portions, the inner of which is 

 the softer. A good example is afforded by Bibio hortulanus, for here 

 the difference between the parts of the " female eye " are not so 

 much marked as in the " male eye," which is of more complex 

 constitution. 



3. Number and position of the retinula cells of Musca, Culex, and 

 Bibio. — The author supports Grenacher, as against Ciaccio and 

 Hickson, in finding that the number of retinula-cells correspond to 

 that of the rhabdomere. In Musca vomitoria the central retinula-cell 

 has the form of a knife with the edge directed towards the centre of 

 the retinula ; the rhabdomere is placed on the edge, and this edge 

 itself is at about its middle converted into a similar substance with 

 it. As Hickson has stated, the nuclei of the other six retinula-cells 

 lie at the distal end of the retinula ; that of the seventh cell is not 

 somewhat deeper, but in M. vomitoria is at the same level as the 

 other cells. In Cidex and Bibio the central rhabdomere is invested 

 in a layer of pigment. 



4. Ocelli of Diptera and Orthoptera. — Generic differences in the 

 minute anatomy of the eyes have been detailed ; the Orthoptera may 

 have accessory eyes, or they may be rudimentary, or merely repre- 

 sented by simple white spots. Among the Acrididae the young have 

 bud-like organs which project a little way beyond the surface, and 

 are comparable to the similarly named structures in vertebrates. 



Gustatory Apparatus of Coleoptera.* — M. J. Gazagnaire has 

 studied the gustatory apparatus of Coleoptera chiefly in the family 

 Dyticidas. He finds on the ventral surface of the labrum, and on 

 either side, a conical swelling the apex of which carries a small 

 chitinous "button" which projects into the buccal cavity; these 

 buttons are hollow, their outer surface carries a number of modified 

 hairs, hyaline in appearance, and provided with a central canal. At 

 the base of the hair (at the periphery), there are about six chitinous 

 canaliculi, which are the excretory ducts of unicellular hairs ; the 

 hair is distinctly lubricated. The branch of the labral nerve can be 

 traced to the base of the button, into which five nerve-fibrils penetrate. 



* Coraptes Rendus, cii. (188G) pp. 629-32. 

 Sor. 2.— Vol. VI. 2 F 



