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



48, very distinct ; the second 46*25 — 45, less marked but distinct ; the 

 third 43 — 42, very indistinct ; the violet end absorbed at 41. In all 

 but the best light the violet end was absorbed to 43, and the third 

 band ceased to exist separately. A thickness of 8 mm. tends further 

 towards this absorption to 43, and the chief band extends to 50*5, or 

 even a little further. The spectrum was the same in blood from all 

 varieties. An alcoholic extract (90 per cent, spirit) of a grey variety 

 was bright orange -yellow, and gave nearly the same spectrum as the 

 blood, except that the bands were shifted to the violet end, and the 

 third faint band was absent. The spectrum was : chief band 49 — 47, 

 second 45*5 — 44, violet end absorbed to 42. The extract was ex- 

 amined in a thickness of 23 mm. and 9*5 mm. 



A drop of water was placed upon a cover- glass and the latter was 

 inverted upon the yellow back of a living pupa of P. Machaon, which 

 was then examined by reflected light, being entirely opaque. The 

 following spectrum was indistinctly seen : — A band in the red (very 

 faint) 65—63, the chief band 49—47, the second 45*5—44, the violet 

 end being absorbed to 42. The green parts of the same pupa, 

 similarly treated, gave the following results : — 69 — 64 in the red, 52 — ■ 

 48. Pieces taken from the yellow parts of the pupal covering gave 

 a similar spectrum to that above described when strong sunlight, con- 

 centrated by an Abbe's condenser, was passed through them; the 

 green parts were more opaque, but the spectrum gave the chief bands 

 distinctly. However treated, the spectra of the derived pigments still 

 contained in the pupal covering are very indistinct. This is probably 

 due to the nearly solid condition in which the pigments exist in 

 association with some animal basis. The alcoholic extract of the 

 covering, with its internal surface carefully washed to remove 

 adherent blood, &c, gradually becomes yellow with dissolved xantho- 

 phyll. The green parts, carefully washed, dried, and placed in carbon 

 bisulphide, gave a yellow solution with a slight greenish tinge, which 

 gave this spectrum in a thickness of 24 mm. Band in the red 70 — 

 66, chief band in the blue 51*5 — 48, the violet being absorbed at 44. 

 These appearances were indistinctly made out in bad light. 



(j.) The Pupa of Ephyra Punctaria. — The pupa is green anteriorly, 

 especially on the wings, and examined as an opaque object by means 

 of Abbe's condenser (and a stop which blocked the central rays), with 

 good sunlight, the following spectrum was seen : — Band in the red 

 70 — 65, a faint but distinct band 63 — 61, and the band 48 — 52, or 51 

 when the slit was widened ; the violet absorbed at 43. This spectrum 

 is remarkable as being the only instance yet observed in which the 

 second band from the red end, of true chlorophyll, was seen separately, 

 and occurred in the right order. For in all other pupae and larvae 

 the third band appeared after the first, and then the second as a 

 shading connecting the former two. The colour is entirely due to the 



