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



been recently acquired, and in consequence of the complete opacity, 

 there would be no advantage in losing the colour of the blood. 



It therefore appears that we must add a fourth class to the three 

 spoken of by Dr. MacMunn (" Proc. Roy. Soc," vol. 35, p. 387) :— 

 " In addition to the classes of chlorophyll-containing animals men- 

 tioned by Greddes, namely those which vegetate by their own intrinsic 

 chlorophyll and those which vegetate ' by proxy,' so to speak, or 

 by means of parasitic algae, a third class must now be added : those 

 which contain enterochlorophyll in their livers, or other appendages 

 of the enteron." This fourth class comprises those animals which 

 make use of a modified chlorophyll (and other plant pigments) 

 derived from their food, because of the protective colour which they 

 acquire from its presence in their blood or tissues. 



12. Notes upon the Physiology and Chemistry of the Blood of Larvce 



and Pupm. 



Some interesting points came out incidentally during the course of 

 this investigation, and they are therefore mentioned, but only as a 

 preliminary treatment of the subject which I hope to examine more 

 completely during the present year. Much of this section is only 

 suggestion. 



'Reaction. — The blood of all larvae and pupae examined (of all 

 colours) was acid to litmus-paper, turning it distinctly reddish, with 

 the exception of JE. Punctaria, which seemed to be neutral (although 

 only one specimen was examined). The acid which appears to be 

 volatile can be extracted with ether, but I have not been able to 

 obtain sufficient quantities of blood (during the winter) to determine 

 what acid is present. The precautions previously detailed show how 

 impossible it must have been to obtain any accidental mixture with 

 digestive secretions. Besides, I have tested for the reaction of the 

 blood upon a great many occasions, and again and again upon the 

 same species. The corpuscles are well known to be amoeboid, and 

 Professor Schafer tells me that as far as he is aware this is the only 

 instance of their occurrence in an acid fluid. 



Coagulation. — The blood clots after a very variable period of time, 

 but generally darkens in about five minutes, ultimately forming a 

 solid black clot which is due to oxidation. If blood be sealed in a 

 tube, the small quantity of oxygen present will form a thin black film 

 on the surface of the blood, and the action then ceases. I have 

 already shown how blood can be kept indefinitely without clotting 

 in a section of tube with a cover-glass over one end, and the other 

 cemented to a glass slide. I have kept the blood of P. Buce- 

 phalus in this way for a month, quite unchanged, and on then 

 breaking off part of the cover-glass a thick black crust was formed 



