URINARY SECRETIONS. 245 



emitted by a circular hole that opens externally a little 

 behind the aperture of the oviduct.* The Doris ejects a 

 sjmilar milky fluid, which, however, comes from the liver, or 

 from a gland so intimately associated with it as not to be 

 separated by any dissection, f The position of this secretory 

 organ is singularly modified in the family Eolidse, where it 

 is found within the apices of their dorsal papillae, distri- 

 buted in correspondency with the disintegrated condition of 

 the liver. The organ, first discovered by Messrs. Alder and 

 Hancock, is "a small ovate vesicle, which communicates 

 with the biliary gland by means of a slender canal below, 

 and at the opposite and narrower end opens externally 

 through a minute aperture at the extreme apex of the 

 papilla." It is filled with elliptical bodies and globules of 

 various sizes, imbedded in a' mucus-like water ; and these 

 contents are, from time to time, expelled as it were by a 

 convulsive contraction of the vesicle. Immediately on ex- 

 pulsion into the circumfluent water, the elliptical bodies 

 burst the little bags in which they are packed in parcels, 

 and shoot out each a long hair-like tail, as they are being 

 scattered abroad. On one occasion our distinguished friends 

 " observed an individual of Eolis picta, when moving freely 

 about, suddenly, and by a convulsive effort, eject from the 

 points of the papillae a minute stream of milk-white fluid, 

 which curling upwards, mingled with the surrounding liquid, 

 and was soon lost to view. The fluid exactly resembled the 

 contents of the ovate vesicle when forced out by pressure, 

 and examined with a lens of low power." J 



In some univalved mollusca, a urinary discharge has been 

 more positively ascertained. Swammerdam detected in the 

 snail a little oblong triangular part, placed near the heart, 

 which he calls the " sacculus calcareus." This organ has a 

 pretty large duct, which runs into the intestine ; and Swam- 

 merdam believes it to be a gland whereby the calcareous 

 matter of the blood is drained from the body, and deposited 

 in the intestine ; " and accordingly we find that such a 

 matter is sometimes mixed with the excrements. " The 

 organ is found, in a modified shape, in many other mollusca ; 

 and some naturalists 1 1 have imagined that the shell was 



* Cuvier, Mem. ix. 24. f Cuvier, Mem. v. 16. 



t Monog. Nudib. Moll, part iii. pi. 7 and 8 ; Arm. and Mag. N. Hist, 

 xv. 82 ; Nordmann in Ann. des Se. Nat. (1846), v. 124. 



Book of Nature, 49. 



|| "The formation of the calcareous matter of their shells, which takes 

 place in a peculiar viscus lying near the heart (sacculus calcareus, Swamin. 

 glandula testacea, Poli"). BLUMENBACH'S Man. Comp. Anat. 251, transl. 



