EGGS OP IXSECTS. 605 



covered by minute rings, of which the ends somewhat over- 

 lap. These rings are thought to be identical in their 

 character with the whitish substance which exudes through 

 pores on the under-side of the body ; and it is more than 

 probable that these layers of rings and their arrangement 

 account for the beautiful prismatic hues which they pre- 

 sent when viewed as opaque objects under the microscope, 

 and by the aid of the side-condenser. This white sub- 

 stance, it should be observed, becomes a part of the intimate 

 structure of the egg-shell, and is in nowise affected by 

 either strong spirit or dilute acids. Sir John Lubbock 1 

 states that in the greenish eggs of Phryganea, " the colour 

 is due to the yolk-globules themselves. In Coccus, how- 

 ever, this is not so ; the yolk-globules are slightly yellow, 

 and the green hue of the egg is owing to the green granules, 

 which are only minute oil globules. When, however, the 

 egg arrives at maturity, and the upper chamber has been 

 removed by absorption, these green granules will be found 

 to be replaced by dark-green globules, regular in size, and 

 about 1 -8000th of an inch in diameter, and which appear 

 to be in no way the same in the yolk of Phryganea eggs." 

 Another curious fact has been noticed, which partially 

 bears on the question of colour : the production of parasite 

 bodies within the eggs of some insects. In the Coccus, for 

 instance, parasitic cells of a green colour occur, " shaped 

 like a string of sausages, in length about the 1 -2000th of 

 an inch by about the I -7000th in breadth." 



The eggs of Moths and Butterflies present many varying 

 tints of colour ; in speaking of this quality we do not re- 

 strict the term solely to those prismatic changes to which 

 allusion is so often made, and which are liable to constant 

 mutations according to the accident of the rays of light 

 thrown upon them ; but we more particularly refer to the 

 several natural transitions of colour, the prevailing tints 

 of which are yellow, white, grey, and a light-brown. In 

 some eggs the yellow, white, and grey are delicately blended, 

 and when viewed with a magnifying power of about fifty 

 diameters, and by the aid of a side-reflector (parabolic- 

 Deflector), present many beautiful combinations. The 

 aiost delicate opalescent or rather iridescent tints appear 



a) Phil. Trans. 1S0, p. 341. 



