296 Mr. E. B. Poulton. Essential Nature of the [Apr. 23, 



the liquid becomes blue, and ultimately black, from the formation of 

 coagulum. The proteids are decolourised and sink, the alcohol remain- 

 ing yellow with xanthophyll (the chlorophyll disappearing) . Absolute 

 alcohol does not lie on the top of the blood, but mixes with it at 

 once. 



Chloroform behaves in the same manner as ether, but it dissolves 

 nothing coloured from the green coagulum ; the latter contracts in a 

 few hours, and a clear blue liquid appears between it and the sides of 

 the tube. The exposed surface of the coagulum (the chloroform 

 having sunk to the bottom) rapidly becomes black. 



Distilled water, like weak spirit, lies on the top of the blood with a 

 cloud of precipitated proteid (probably globulin) above the junction. 

 On shaking, the cloud disappears, and the blood only seems diluted ; 

 if now more water be added (altogether many times the volume of 

 the blood), in a few minutes the whole fluid becomes cloudy, remain- 

 ing dark greenish. On filtering, a blue solution comes through, 

 which slightly darkens for some hours. With less water the blood 

 coagulates normally, although after a longer interval of time. 



Carbon disulphide had no effect for a considerable time. Eventually 

 the blood was coagulated (green) but nothing coloured was dis- 

 solved out. 



Heat. — The blood of the pupa of 8. Ligustri was heated in a glass 

 tube in a water-bath; no change was seen till the temperature 

 reached 132° I\, when part of the blood became slightly dim. By 

 141° the whole of the blood was distinctly cloudy, but it was not till 

 180° that the blood became quite coagulated — solid-looking and 

 opaque, the proteids being yellow with xanthophyll. In the in- 

 terstices of the clot was a clear yellow fluid. The xanthophyll in the 

 coagulum was easily extracted by ether or alcohol. 



13. The Relations between the Colour of Phytophagous Itarvoe and that of 



their Food-plants. 



Entomologists have been long aware of the fact that the colours of 

 many larva? vary (within the limits of the same species) according to 

 the colour of the plant upon which they are found. This is especially 

 true of larvae feeding upon brightly- coloured parts of the plant, such 

 as the anthers or petals. At the same time there has been hardly any 

 investigation of these interesting facts. The numerous instances in 

 which such variations have been observed are, T believe, exhaustively 

 recorded by Mr. Raphael Meldola in the editorial notes to his trans- 

 lation of Dr. Weismann's " Studies in the Theory of Descent " (the 

 essay on the Origin of the Markings of Caterpillars), and in a paper 

 in the "Proc. Zool. Soc." for 1873. 



The first step m this investigation is to make quite certain of the 

 facts by feeding a sufficient number of larva?, from the egg, upon the 



