130 THE ANATOMY OF THE HONEY BEE. 



transformed into the crystalline rod. The cornea is secreted by the 

 corneal pigment cells, which at first lie distal to the cone, and possibly 

 also by the outer pigment cells. The nerve fibers are formed as 

 differentiated parts of the retinulae which penetrate through the base- 

 ment membrane (fig. 54, BM) and enter the retinular ganglion be- 

 neath it at the outer end of the optic lobe of the brain. Hence the 

 retinulae are simply sense end-organs of the skin comparable at an 

 early stage of their development with other sensory epidermal cells, 

 and we thus see how a simple layer of epithelium may be transformed 

 into such an immensely complex organ as the compound eye. 



There has always been a great deal of discussion as to how insects 

 see by means of the compound eyes. The weight of opinion now 

 favors the theory that they see a part of the object or field of vision 

 with each ommatidium. But it is most certain that, at best, most 

 insects see very indistinctly, and, in fact, it is often questioned 

 whether they really see the shape of objects at all or not. A few of 

 them, however, such as dragonflies, appear to have a very acute 

 vision. In the case of the honey bee there is yet much difference of 

 opinion as to whether the workers discover nectar by the bright color 

 of the flowers (i. e., by the sense of sight) or by the sense of smell. 

 The sense of sight in bees and in insects generally, however, may be 

 found elaborately discussed in many books dealing with the senses of 

 insects. 



The simple eyes or ocelli (figs. 9 A, 10, 52, and 53, 0) are con- 

 structed on quite a different plan from that of the compound eyes, 

 each consisting of a lenslike thickening of the cuticle back of which 

 the epithelial cells are specially elongated, and sensitized by nerve 

 connections. The ocelli of the bee, however, have never been care- 

 fully studied. 



XI. THE E.EPE.ODUCTIVB SYSTEM. 



The reproductive organs are those that produce the cells from 

 which new individuals are formed. All animals grow from at least 

 one cell called the egg and almost all from a combination of the egg 

 with another cell called a sfermatozoon. The uniting of these two 

 cells is called the fertilization of the egg. In a few animals the two 

 different kinds of reproductive cells are -formed in the same individ- 

 ual, but in most of them, including all insects, the sperm and the eggs 

 are produced in different individuals — the males and the females. 

 In the honey bee the males are called drones, while the females are 

 called queens or workers, according to their functions in the hive. 

 The queens have the egg-producing organs or ovaries greatly devel- 

 oped, while these organs are rudimentary in the workers. The single 

 active queen in each hive, therefore, normally produces all the eggs 

 of the colony, while the work of rearing and providing for the brood 



