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BULLETIN OF THE BUREAU OF FISHERIES 
The osphradia of Pecten are very inconspicuous structures and, in these investi- 
gations, have not been positively observed. The osphradial branches of the osphra- 
dio-branchial nerves arise just ventral to the kidneys. (See fig. 14.) Dakin (1910) 
found no evidence of an olfactory or other sense in these organs of Pecten. On the 
other hand Copeland (1918) found that certain predacious gastropods responded 
definitely to olfactory stimuli but failed to respond after the osphradium had been 
removed. 
The eyes and tentacles have been described with the mantle. 
URINOGENITAL SYSTEM 
The urinogenital system comprises ovaries, testes, pericardium, and kidneys. 
The ovaries are located in the ventral or tip portion of the visceral mass and are, 
when eggs are present, pink or even red. The white or cream colored testes occupy 
that portion of the mass dorsal to the ovaries and ventral to the stomach and also 
extend, anterior to the mid-gut, along the outer edge of the mass well toward the tip. 
Occasionally “islands” of ovarian tissue are to be found within the limits of the 
testes, and vice versa. Rarely organs of one sex are so greatly extended as to make 
the individual appear unisexual. The general position of ovaries and testes is shown 
in Figures 10 and 11, and something of the microscopical structure of an ovary in 
Figure 15. 
Credit for the discovery that the sexual organs of Pecten open through the kidney 
is given to Garner (1841). Lacaza-Dutliiers (1854) figured a common duct to take 
both eggs and sperms to the kidney, through which they are discharged. The pas- 
sages are somewhat hard to follow, but have been traced by Dakin in serial sections 
and demonstrated by gently pressing the ripe gonads so that masses of eggs or sperms 
are seen to emerge from the kidney. 
The renal organs, or kidneys, are asymmetrical lozenge-shaped organs, generally 
light brown in color and located on the adductor muscle (figs. 4 and 11), one on 
each side of the visceral mass in the angle formed with the branchial axis. They 
are well supplied with blood vessels. The lumen is much branched. The walls are 
glandular (see Kellogg, 1892; Drew, 1906; Dakin, 1909) and ciliated (but see Dakin, 
loc. cit.) . Urea is given off in solid concretions (Pelseneer, 1906) which have been 
figured for P. irradians by Kellogg (1892). An elongate, lipped urinogenital aperture 
is located at the ventral end of each kidney, near the visceral ganglia. Dakin states 
that the two kidneys communicate one with the other at their dorsal ends through a 
transverse duct lying between the visceral mass and the adductor muscle. 
It seems to be well demonstrated that the pericardium communicates with each 
of the kidneys and forms part of the excretory system (Pelseneer, 1906; Drew, 1906; 
Dakin, 1909). I have failed to find the reno-pericardial openings in P. irradians 
or even to demonstrate them by means of red pericardial injections. In some in- 
stances a red kidney was thus obtained, but in no instance did the red fluid appear 
at the urinogenital aperture, which is taken to mean that in some manner the blood 
spaces of the kidney received the injection. Although Drew apparently found the 
openings without difficulty in the large sea scallop, Dakin failed to demonstrate 
them by injecting the kidneys and was only able to make them out by serial sectioning. 
In the case of the scallop the excretory function of the pericardium is stated to be car- 
ried out by the walls of the auricles, which are uneven, somewhat spongy, and of a 
yellow color. 
