52 SAMUELSON;, ON THE HONEY-BEE, 



" 1. From tlie exceptional cliaractcr of hexagonal or any oilier than cir- 

 cular lenses iu the eyes of all animals, and from the fact of the simple eyes 

 of insects themselves \mns ci/nchtr. 



"2. From tlie circumstance that, in tiie insect races, the conical lenses 

 of the ocelli (to be described presently), which do noi impinge one upon 

 another, are not hexagonal but rouiu!. 



"o. Because in the ])osterior angle of the compound eye of the worker- 

 bee we often find some of the corneal or external lenses of a smaller size, 

 and not adherent, but having a lilile iatenncdiate space surrounding each, 

 and these facets are imariahly round. 



" Fron\ the fact that in one inject at least,- the sheep-tick {Melophoffux 

 ovii/us), which ranks very low in the scale of development, we find all the 

 external facets of the compound eyes non-adherent and circular.* 



" So much, then, for the corneal lens of the ocellus of the Bee, a com- 

 pound hexahedral prism with double convex surfaces. Following the course 

 of a ray of light after it has passed through this lens, we find that it tra- 

 verses a vacant space before entering the conical lens, this space being sur- 

 rounded by the dark pigment already referred to, and constricted or nar- 

 rowed midway into the form of a round hole, on the same principle as the 

 diaphragm in the eye-piece of a microscope or in the Coddiugtou lens. 



"This natural diaphragm is so formed, that the amount of light which 

 is permitted to pass is to some extent limited, and any remaining tendency 

 to abernitiou in this wonderful instrument is thereby completely corrected. 

 The same layer of dark colouring-matter is continued downwards betw^een 

 the conical lenses, so that these are effectually isolated, and the raj's cannot 

 become confused by passing from one lens to the other. The conical lens 

 is curiously shaped, but simple in its structure, not being compound, as is 

 the corneal lens, but of the same density throughout. It is also double 

 convex, the base as well as the apex (from which the point is removed) pre- 

 senting rounded surfaces. 



"At the apex it comes into contact with the bulbous expansion of the 

 optic nerve, which receives the image of the external object, and this nerve 

 proceeds downward in a line continuous with the axis of the ocellus, until it 

 meets the nerves of the other eyelets. These then unite and form a com- 

 mon trunk that communicates with what we may popularly call the insect's 

 brain (strictly speaking, the 'cephalic ganglia^). • 



"But you may, perhaps, be puzzled to understand how so many small 

 images, as must necessarily enter the compound eye of the Bee, can become 

 amalgamated and combine to form a single picture of the external field ; 

 the effect will, however, be perfectly clear to your mind, if you only con- 

 sider the action of our own two eyes, which convey to our brain not two, 

 but only one distinct image of the surrounding oijjects ; and supposing 

 that, instead of two, we had a considerable number of eyes properli/ dis- 

 posed, the ultimate effect would be just the same. Now, an examiuation 

 of the external lenses of the compound eye of the Bee shows that their 

 surfaces, especially the inner ones, are not all of equal convexity, and 

 there appears to be, as we might expect, such an arrangement and disposi- 

 tion of the whole mass as to ensure the most jierfect co-operation between 

 each lens and the surrounding ones. We also find regularly scattered over 

 the surface of the cornea — in fact, one between almost every lens and its 

 neighbour — a great number of long hairs, and these also aid, no doubt, in 



* A careful examination, of the eye in the pupa, whilst in process of 

 development, confirms the opinion here expressed. 



