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



The two tubes superposed gave a more marked spectrum, but the 

 need of stronger light was much felt. The dark band broadened, 

 extending towards the red end to 69'5, and past 64 towards the 

 violet, dimming the red, and apparently uniting with the dim band 

 at 60. The edge of this latter was nevertheless slightly darker than 

 the dimmed red. The absorption of the violet end was unchanged. 



The fresh blood of a larva of the same species, which had been 

 bright green (due to its blood), but which after ecdysis became 

 brown, was examined (December 31st, 1884) in a wide capillary tube 

 about 1 mm. in internal diameter. The blood was almost colourless, 

 very faintly yellow, and produced no effect on the spectrum. 



At the same time the fresh blood of another individual of the 

 same species, which was dark greenish-brown, due to a combination 

 of subcuticular pigment and green blood, was examined in a capil- 

 lary tube. 



The compound character of the larval colouring was proved by 

 gentle pressure. The pale green blood with a thickness of about 

 1 mm. gave the band in the red from 65 — 68, the violet end, being 

 completely absorbed at 45, darkened to 51 (when the slit was narrowed 

 so as to render the band distinct). A greater thickness of blood 

 darkened the band, and cut off the violet end at 50, darkening to 52 

 (when the band was distinct). A still greater thickness produced 

 more marked results with nearly the same limits. On widening the 

 slit no blue appeared at the absorbed end. The dark band now 

 seemed to extend to 68'5. The whole spectrum was much dimmed, 

 but this was probably due to the accidental presence of fat in the 

 blood. In this case the thickness of the fluid was 3*3 mm., and the 

 colour was bright green. 



The fresh blood of another individual of the same species, which 

 was of a mahogany-brown colour, due to subcuticular pigment, was 

 examined at the same time. When the larva was gently compressed, 

 it became slightly yellowish-green in the swollen uncompressed part. 

 A thickness of 4"5 mm. was faintly yellowish. > 



The spectrum showed a very faint band in the red, and the violet end 

 was cut off as before, only less sharply and completely. Thus the latter 

 character is more delicate as a test than the former. Hence in this 

 considerable thickness there was far less effect than that produced 

 by the blood of the last individual in a capillary tube. After being 

 exposed to the air for 2^ hours the blood became brown, but there was 

 no difference in the spectrum. 



Another brown individual of the same species was examined at 

 the same time. When gently compressed it emitted a clear green 

 fluid from the mouth, exactly resembling the blood of a green indi- 

 vidual in its colonr and transparency when examined in a thickness of 

 2'25 mm. (except tnat this was a little darker). 



