82 A V.WT.V, ON EGGS, 



solution obtained from egg-spots by alcohol and an acid. Tims, 

 all three give a band in the middle part of the red, and a hazy 

 cloud from the beginning of the blue to the violet end of the 

 spectrum ; but the depth of tint in these bands is very variable, 

 and in no case have the bands a distinct outline. The spectro- 

 scope fails, in this instance, to give any sure indication ; but it 

 is worthy of notice that blood, which has been thoroughly de- 

 oxidised by the action of phosphui-etted hydrogen gas, gives a 

 spectrum like the spectra obtained from the three substances 

 above mentioned. The band in the red is a little nearer to 

 the orange. That is all. The hazy cloud fi'om the blue to the 

 violet being the same." 



yil. Considering, therefore, the high degree of probability 

 that has been established under the fourth head of this paper, 

 and the results of the spectroscopic and chemical researches 

 as t^bove given, and which seem decidedly, but perhaps not so 

 strongly as could be. desired, to con'oborate tliat probability, it 

 may be concluded, without undue partiality, (1) that the vari- 

 ous ground colours which distinguish eggs are owing to different 

 states more or less approaching to, if they be not actually inflam- 

 mation of the lining membrane of the oviduct, and giving rise 

 to the different coloured albumina seen in the *' white" and in 

 the shell. And (2) that the various markings on the ground 

 colour of the shell, whether on the surface or on deeper layers, 

 are the result of irregular escapes of blood from the turgid and 

 ruptured blood vessels of the same membrane, under i)ressure 

 exerted by tlie muscular coats of that tube, upon the cg:g more 

 or less coated with rough shell ; the blood being catalysed or 

 altered to chlorophyll, or colouring matter as actually found in 

 the bile both of the Ox and the Peewit. 



Afl before stated, no pigment glands have ever been described 

 OS existing in the oviduct. I have looked in vain for them in 

 the oviduct of the Rook and the Peewit, both of which lay 

 higlily coloured eggs. 



AVe may conceive it possible tliat tlie cells of the delicate cel- 

 lular tissue wliich becomes organised in tlie Hrpiid i>l:i^f("r of flic 



