THE SILKWORM ITS FORM AND LIFE HISTORY. 29 



back, but below we observe the three pairs of legs, each of which 

 indicates a separate segment. The prothorax, or first thoracic 

 segment, which is a small one, carries only a pair of legs ; the 

 second, or mesothorax, much the largest of the three, is better 

 provided, and carries a pair of legs below and a pair of wings 

 above ; and the third, or metathorax, is similarly furnished, and 

 carries the third pair of legs below, and the second pair of wings 

 above. This disposition of parts is not confined to the silkworm, 

 but is common to all insects ; legs and wings are not attached 

 indiscriminately to any part of the body, but are always arranged 

 as above on the three thoracic segments. 



Few parts of the body are more elegant than the antennae ; 

 they are well worthy of a minute and careful investigation, and 

 indeed, the more minutely we examine them the more do we see 

 to admire. Each consists of a white central axis, carrying along 

 almost its entire length two rows of long blackish threadlike pro- 

 jections, which slope downwards away from the white axis like 

 the sides of the roof of a house from its ridge, the individual 

 threads becoming shorter as they reach the end of the antenna, 

 and dwindling away at last to nothing, so that the organ terminates 

 in a point. This is all that appears to the naked eye. But place 

 the object under the compound microscope, and you will be 

 astounded at the complexity of structure it manifests. The white 

 axis is now seen to owe its colour to tiny snow-white scales 

 packed close along its upper surface, and concealing its really 

 dark exterior. It is not a simple rod, but is composed of 

 a series of fifty minute joints, which, by their power of moving upon 

 one another, give extraordinary flexibility to the whole. Each of 

 these carries two long thin projections, far longer than itself, 

 which are themselves also doubly fringed with hairs of extreme 

 tenuity. These long processes constitute the double row of 

 threads spoken of above. Antennae of this kind are said to be 

 " pectinated," i.e., comblike. Conjecture is vain as to the use of 

 these organs. They are no doubt organs of sense of some kind, 

 but of what sense or senses is a great puzzle. Several different 

 functions have been assigned to them, with varying degrees of 

 probability, and it is impossible at present to come to any definite 

 conclusion in the matter. 



The antennae are attached to the head just outside two great 

 black hemispheres, which are evidently the eyes. The surface 

 of these, under magnification, reveals a network of 'hexagonal 

 divisions, each of which is the outer boundary of a complete 

 organ of vision, so that these two rounded masses are not, what 

 at first sight they seem to be, simply two enormous eyes, but each 



