Nos. 45>-452.] '-^^'/^'^/^'-^^V S()CJJ-:T\- (>/■ ZOiUjHUSTS. 321 



Bee: E. F. Phillips, University of I'cniisylvania. - The oinma- 

 tidia which make up the compound eve ot the hone\ bee arc 

 each composed of a crystalline cone of four cells and a rhalxlome 

 surrounded by eight or occasionally nine retinular cells. l-:ach 

 ommatidium is sheathed by two kinds of pi,<;ment cells, the inner 

 pigment cells, two in number which surround the base of the 

 crystalline cone and the outer pigment cells, twehe in number 

 which extend the entire length of the onnnatidiuni. luu h ret in- 

 ula cell sends in a process to the retinular ganglion whit h has 

 the property of a nerve fibre. The ner\e fibres of the c\ e aie 

 differentiated portions of the retinular cells which scud in tine 

 branches to the rhabdome, which is j^obably the ncr\e ending 

 of the eye. There is no connection between the crystalline cone 

 and the rhabdome and the cone has not a sensory function. 



The ommatidia develop from a single layer of thickened hypo- 

 dermis and the region of the compound eye is marked out in the 

 unhatched larva. The first indication of ommatidia is the 

 grouping of cells with a distinct boundary in young larvae. The 

 cells of these groups become differentiated until each grou]) is 

 composed of a spindle-shaped mass with large nuclei, surrounded 

 by numerous cells with smaller nuclei. The central spindle 

 forms the retinula and the rhabdome is early visible as a clear 

 space at the outer surface. The crystalline cone arises from the 

 sides of the retinula and the pigment cells are still hirther out. 

 The ommatidium is formed as a morphological in\ agination of 

 the hypodermis as was held by Watase. The rhabdome and 

 crystalline cone are formed as intracellular secretions and the 

 lens is secreted by the inner pigment cells whose nuclei m the 

 young pupal eye are distal to the cone and afterward nngrate to 

 the base of the cone. 



