i6o PHYSIOLOGY OF THE INVERTEBRATA. 



canal of another brown individual of the same species showed 

 a band in the red from 65.5-68.5, while the blue was cut off 

 at 50, darkened to 52. 



Poulton remarks that " this observation upon the green 

 fluid from the digestive tract is important, because it serves 

 to identify the chlorophyll in the blood with that taken in as 

 food. It is likely, however, that a greater thickness of fluid 

 and the use of sunlight would bring out some differences 

 between the derived pigment dissolved in the digestive secre- 

 tions, and that united with a proteid in the blood 



It seems quite certain that the derived pigments of the blood 

 and tissues are only protective, and play no further part in 

 the physiology of these organisms. Thus there are no 

 marked differences between the physiological processes of 

 the brown and green individuals of the same brood in a 

 dimorphic species, or in the processes of a green larva, which 

 has become brown, or vice versa. It seems that the pigments 

 are entirely harmless, and are often retained when they would 

 have no effect upon colour. Thus, in Pygmra BucepJudiis, 

 the blood is bright green, although the larva and pupa are 

 entirely opaque, while the eggs are white. It is possible 

 that in this case the conspicuous colours — which warn enemies 

 that the species is distasteful — have been recently acquired, 

 and in consequence of the complete opacity, there would be 

 no advantage in losing the colour of the blood." 



In the experiments just mentioned, Poulton used a paraffin 

 lamp as a means of illumination, but he afterwards found 

 that by the aid of sunlight the spectra were further developed. 



The concentrated green blood of the larva of P. meticulosa, 

 when examined by sunlight, gave the spectrum represented 

 in Fig. 31, sp. I. "The band in the red, reaching from 

 64.5-68, was very black, except at the edges. When this 

 band was most distinct and clear, the violet end was absorbed 

 to 51, darkened to 52. On opening the slit a little, the blue 

 came through (though dimmed) at 48, the violet end being 

 absorbed at 43. When the slit was very narrow, traces of 



