ON THE PAIRED NEPHRIDIA OF PROSOBRANOHS. 621 
duct. In higher developed forms the glandular portion of the 
right kidney has disappeared, whilst its duct forms a part of 
the proper genital duct. 
For the present I can only say that, contrary to v. Jhering’s 
and B. Haller’s assertions, there is no proper genital duct in 
Turbo and Trochus. 
Naples ; June 1, 1892. 
EXPLANATION OF PLATES XXXVI and XXXVII, 
Ilustrating Dr. R. v. Erlanger’s paper “ On the Paired 
Nephridia of Prosobranchs.” 
List of Reference Letters. 
A. Anus. 4p. Anal papilla. dz. Auricles of the heart. aur. Right ; 
aul. Left auricle. ao. Aorta. B. Gill (ctenidium). Br. Right; B/. Left 
ctenidium. as. Basibranchial sinus. 4s. Branchial rod or support. C. 
Reno-pericardiac canal. #. Hye. F. Foot. 7%. Mantle-fissure. G. Gonad 
genital gland. Gd. Genital duct. H. Visceral hump. Ha. Heart. J. In- 
testine-gut. JZ. Liver. M/. Mantle cavity. Ma. Mantle. Md. Bottom of 
the mantle cavity. Msr. Right superior portion; Ms/. Left superior portion ; 
Mir, Right inferior portion; M7. Left inferior portion of the mantle cavity. 
muc. Mucous gland. mw. Muscle. NV. Nephridium. Jr. Right; WZ. Left 
nephridium-papillary sac. P. Papilla of the nephridium. Pr. Right; PZ. 
Left papilla. Pc. Pericardium. &. Rectum. S. Stomach. sz. Sinus. V. 
Ventricle of the heart. ve. Vein. of. vena transversa. vde. Branchial 
efferent vein. X. External opening of the nephridium. Xz. External open- 
ing of the right; X/. External opening of the left nephridium. Y. Opening 
of the nephridium into the pericardium. y. Opening of the reno-pericardiac 
canal into the pericardium. 
Fie. 1.—Dorsal view of Haliotis tub. after removal of the shell. 3. 
Fic. 2.—Dorsal view of Haliotis tub. The mantle cavity has been 
opened, the rectum and the mucous gland thrown back, so as to display the 
external openings of the kidneys. 1. 
Fic, 3.—Pericardium of Haliotis tub. opened; heart removed. The 
