30S Sir Everarb Home on tlie formation of fat 
matter of the lobster, in the course of sbme clays becomes of . 
an oehraceous colour. In this state it seems to be permanent, 
for it was retained by linen which had bben marked with it, 
after repeated boiling in water and washitig with soap. 
From these cursory experiments, Mr. HXf chett observes, 
that this animal colouring substance is apparently of a pecu- 
liar nature, and that it is the same in the confmbn cray fish and 
the prawn, as well as in the sea Cray fish and the crab, but in 
the two last, it has already assumed its red colour. 
That the ova of the salmon and pike Have no yelk, and 
consist principally of albumen, as they Coagulate by heat, 
perhaps is a sub- 
a small portion of oil, 
a odi oJni boariebnoo 
but contain 
stitute for yelk. 
as those of 
the lizard and snake, have a regularly formed yelk, like that 
of the hen, composed of the same ingredients; but in both the 
viviparoUs afid oviparous sharks there is no perfectly formed 
albumen, but^n^lf^Sci^i which Mr. 
BrXnde ascertained to be intermediate between gelatin and 
m 
inter 
albumen, similar to what is met with irf the spawn of the 
B£n " 8 ^ 98 tbomoJauooB 9 ib s 
In addition to that which haAW® f i^^e^stated, Mr. Hat- 
has communicated to me the follb^bim observations. 
u The yelk of the eggs of birds is principally and essen- 
tially composed of a butyraeeous oil, combined with a small 
proportion of albumen, the average of which in the yelk of 
the common fowl amounts to about one fifth. Yelk, when tri- 
turated and diluted with water, forms (as is well known) an 
emulsion, and yelk may be regarded as an emulsion in a high 
state Of concentration. 
