374 Dr. Burnett on the Renal Organs of the Vertebrata 
This increase in bulk could have -been effected in no other 
way than by an absorption of materials furnished by the dermal 
sac, since the existence of an operculum would prevent the en- 
trance of nutritive matter from without. The gelatinous matter 
which originally surrounded the egg, may have contributed some- 
thing, but still there is growth after this has disappeared. It 
seems highly probable, therefore, that the walls of the, pouch se- 
erete the necessary additional quantity to supply all that is re- 
quired for development. In so far as observation has extended, 
this is a solitary instance among Batrachians if not among Rep- 
tiles generally in which the embryo is nourished at the expense 
of materials derived from the parent 
Eanes 
Arr. XL.—Researches on the Development and intimate Struc- 
ture of the Renal Organs of the four Classes of the Verle 
brata ; by W. 1. Burnett, M.D., Boston. 
Tere are two facts strikingly indicative of the importance of 
the urinary organs in all the higher forms of animal life. 
are: first, their widely distributed presence; and second, 
early appearance in developing embryonic forms; I might, iI 
haps, add as a third fact, that their functional activity Js usually 
in pretty exact ratio with the grade of organization. sill 
Throughout the higher classes of the Invertebrata,* and nae 
the Vertebrata, these organs are present, and their functional re 
lations quite prominent ; it is only in the lower classes of nine hs 
imal kingdom, where there is an absence or incompleteness © : 
in which, as also ip 
ns Stated eon ko eee 
function, and are often of a complex structure. See Comparative Anatomy, ™ ’ 
bold and Stannius, transl. &e. by Burnett, vol. i, $8 223, 265, 288, 814, 345 
