42 



THE NATURE OF ANIMAL LIGHT 



godes, whose lights are red and greenish yellow, and in the 

 deep sea squid, Thaiimatolampas diadema, which produces 

 lights of three colors, two shades of blue and red. The 

 red light in the case of the squid appears to be due to a 

 red color screen formed by the chromatophores, but in 

 Pliengodes no screen is present. 



As we have seen, difference in color of the light does 

 not necessarily indicate difference in spectral composition 

 because of the Purkinje effect. However, examination of 

 the spectrum of various luminous forms has very clearly 

 indicated that the different colors are really due to light 

 rays of different wave-length and are not the result of any 

 subjective phenomena. To facilitate comparison, spectral 

 lines and colors are given in Table 4. The first adequate 

 observations on the spectra of luminous animals were 

 made by Pasteur (1864), who studied Pyrophorus and 

 found a continuous spectrum unbroken by light or dark 

 bands. Lankester (1868) discovered a similar contin- 

 uous spectrum in Chcetopterus insignis and placed its 

 limits from line 5 to 10 on Sorby's Scale (about A = 0. 55/^1 



Table 4 

 Wave-lengths of Fraiinhofer Lines and Prominent Lines in Line Spectra 



FRAUNHOFER LINES 



