EYE, COMPOUND. 



197 



EYE, COMPOUND. 



c.c. 



-C.C. 



-o.-p.c. 





-ret. 



-rein. 



Fit; 1. 



)m. 



Fi<i. I. — Ommatldiam of adnlt eye 

 of bee: I. lens: c. c. crystalline cone; 

 o. p. c. onter pigment-cells : c. p. c, 

 ••omeal pijjroent-cells. which. In the 

 early stages, secrete the len.s: r. h. b.. 

 chahdome: ret., retlnnia: ret. n.. nu- 

 clei of retlnnia cells; b. m.. basement 

 membrane. 



Fig. 2. — Ommatldlnm of pnpa; let- 

 tering as In Fig. 1: p. g. m.. pigment 

 forming In retlnnia. 

 ' In Fig. 1 the pigment Is not shown 

 In the oater portion of the retlnala 

 cells. 



tising cards, and at the same time give him 

 a little sample of honey to taste. This can 

 be done very readily by handing out some 

 strips of strong manila paper, which are to 

 be dipped in the honey and then transferred 

 to the rnoiitli. 



EVE, COIMFOUND. An examination 

 of the large compound eyes of a bee will 

 show that the outside is made up of hexag- 

 onal areas, thousanfls in number. Each of 

 these hexagons is the outside of one of the 

 elements of which the compound eye is com- 

 posed ; and, since they are all constructed 

 alike, a descrijjtion of one will serve for all. 

 Each of these elements is called an ornma- 

 lidium. If, then, we take a section through 

 one of the compound eyes parallel with the 

 top of the head of the bee we shall get some 

 of them cut lengtfiwise, thereby showing 

 best the structure, although it is also neces- 

 sary to cut other sections at right angles to 

 this plane in order to get the shape of some 

 of the parts. The figures which accompany 

 this show the ommatidium cut lengthwise. 

 Another figure shows an ommatidium from 

 the 2>'<pa stage. 



The outside portion, already mentioned, 

 is the lens layer Z,and is composed of chitin, 

 as is all the rest of the outside covering of 

 the bee. The section shows this cut open, so 

 that only two sides of the hexagon aie shown. 



The next lower structure is the crystalline 

 cone c, c. which is composed of four cells, of 

 which only two show in the long section. 

 In the pupa stage the boundaries are much 

 clearer, and the nuclei larger than they are 

 in the adult eve. This cone is clear, and, 

 like the lens above it. gathers in the light 

 rays so that they can act onthe nerv'es below 

 just as the lens in the human eye gathers 

 together rays of light so they can affect the 

 nerves behind it. 



Directly in line with the cone is a long 

 rodlike structure which runs clear to the 

 bottom of the ommatidium. called the "rhab- 

 dome." rhh. This probably contains the 

 end of the nerves, which are sensitive to 

 light. 



Around the rhabdome are eight retina 

 cells reL which have poured out a secretion 

 while in the pupa state to form the rhab- 

 j dome. 



Around the cone and retina cells there 

 are pigment cells o. p. c. and c. p. c, that 

 keep the light from passing from one om- 

 matidium to the other, and thus making a 

 I confused image, just as the inside of a 

 camera is painted black to avoid reflections, 

 ilnjthe human eye we also find pigment. 



