i8 4 



HA R D WICKE ' S SCIENCE-GOSSIP. 



or by any thoughts, words, or actions, that only a 

 professor could know, the same as a sculptor, or a poet, 

 or any mechanic, thus in a measure identifying 

 that person by their knowledge of the language, 

 either spoken, written, acted, or by motions, forms, 

 by evidence of sympathy, and by that means a person 

 cannot truly sympathise without a true knowledge of 

 the individual, and as human kind a thousand years 

 ago could not understand the variety of languages as 

 now, so shall we accredit this species of entity with 

 enlarging their powers of mental vitality as to even 

 know their ancestry, of their former localities, their 

 former colours, their warlike or peaceful former 

 actions, "per homo genus, omnia." 



The senses of vision in ants and bees. It is, I think, 

 generally assumed not only that the world really 

 exists as we see it, but that it appears to other 

 animals pretty nearly the same as we see it. A little 

 consideration, however, is sufficient to show that 

 this is very far from being certain, or even probable. 

 In the case of insects, moreover, the mode of vision 

 is still an enigma. They have (at least many of them 

 have) a large compound eye on each side, and ocelli 

 generally three in number, situated on the summit of 

 the head. The compound eyes consist of a number 

 of facets, each situated at the summit of a tube, to 

 the base of which runs a fibre of the optic nerve. 

 The structure of the ocellus and that of the compound 

 eye are different, and it does not seem possible that 

 the ocellus should be derived from the com- 

 pound eye, or vice versd. On the contrary both seem 

 to point back to a less-developed ancestry. Starting 

 from such an origin, an increase of the separate 

 elements, and an improvement of the lens would lead 

 to the oculus, while an increase to the number of 

 eyes would bring us to the compound eye. On the 

 other hand there are reasons for believing the 

 different kinds of eyes to be of distinct origin. 



It seems clear that the picture produced by the 

 ocelli must be altogether different from the picture 

 given by the compound eye, and we may 

 reasonably conclude that the two organs have distinct 

 functions. It used formerly to be supposed that the 

 compound eye was for distant vision, and the ocelli 

 for near vision. Claparcedr, however, maintains the 

 opposite theory, while Mr. Lowne regards the ocelli 

 as incapable of producing anything worthy of 

 the name of an image, and suspects that their 

 function is the intensity in the direction of light, 

 rather than vision. The ocelli, or simple eye, sees 

 in the same way as ours do, that is to say the lens 

 throws an image on the back of the eye, which we 

 call the retina. In that case they would see every- 

 thing really reversed as we do, though long ex- 

 perience has given us the right impression. The 

 simple eye of insects thus resembles ours in this 

 respect. As regards the mode of vision of the 

 compound eyes there are two distinct theories. 

 According to one, that is the Mosaic theory of 



Muller, each facet takes in only a small portion of 

 the field, while, according to the other theory, each 

 facet acts as a separate eye. This latter view has 

 been maintained by many high authorities, but it is 

 difficult to understand how so many images could be 

 combined into one picture. Some insects have more 

 than twenty thousand facets on each side of their 

 head. No ants, indeed, have so many, but some 

 there are that have not less than one thousand eye 

 facets. The theory, moreover, presents some 

 anatomical difficulties. Thus in certain cases there 

 is no lens, and consequently there can be no image. 

 In some it would seem that the image would be 

 formed completely behind the eye, while in others, 

 again, it would be in front of the receptive surface. 

 Another difficulty is that any true projection of an 

 image would in certain species be precluded by the 

 presence of impenetrable pigment, which only leaves 

 a minute central image passage for the light rays. 

 Again it is urged that even the sharpest image would 

 be useless, from the absence of a suitable receptive 

 surface, since the structure of the receptive surface, 

 belonging to each facet, seems to preclude it from 

 receiving more than a single impression. The 

 prevailing opinion of entomologists now is that each 

 facet receives the impression of one pencil of rays, so 

 that in fact the image formed in a compound eye is a 

 kind of mosaic. On the other hand, this theory 

 itself presents many difficulties. Those ants which 

 have few facets must have an externally imperfect 

 vision. Again, while the image produced in the 

 retina of the ocellus must of course be reversed, as in 

 human eyes, in the compound eye, on the contrary, 

 the vision on this theory would be direct. That the 

 same animal should see some things directly and 

 others reversed, and yet obtain definite conceptions 

 of the outer world would be very remarkable. But 

 while it is difficult to perceive how ants see, yet they 

 do see. 



C. Pawson. 



DHon. 



COLOURS OF FLOWERS. 



I AM rather surprised to note that none of our 

 botanical friends have had any comments to 

 make upon the two articles in the June number, on 

 the above subject, as it seems to me that there are 

 several points in both, which ought not to be allowed 

 to pass unchallenged. I regret that my own know- 

 ledge of botany is too limited to allow of my taking 

 up the cudgels, yet I venture to make the following 

 remarks, in the hope that some one better acquainted 

 with botany may thereby be induced to enter the 

 ring. 



In the first place, the footnote on p. 134 says, 

 " I cannot call to mind any instance in the works of 

 either Darwin or Wallace, where colour in flowers 



