60 FISH—CULTURAL ASSOCIATION. 
this is the case, if the handle of a scalpel is gently stroked over 
the distended ducts over the side of the body mass of the animal, 
as it lies in the shell, from the head end toward the posterior 
portion below the muscle, the ova, or spermatozoa, as the case 
may be, can be forced out of the, open end of the outgoing 
generative canal into the upper gill or branchial cavity into 
which the former opens on either side, as described in the an- 
atomical outline sketch given in my report to the Maryland 
Commission for 1881, page 15. 
It has recently been asserted by some Dutch investigators that 
the generative products were not discharged by way of a single 
duct on either side of the animal, as described by Lacaze- 
Duthiers. What anatomical grounds these observers have for 
this statement I do not know ; they appear to have been inves- 
tigating the structure of the animal by means of sections or thin 
transverse slices, which they have examined microscopically. 
The simple experiment with a sexually ripe oyster, as described 
above, has invariably given the same result ; never more than a 
single opening was found on either side. In every case the eggs 
were readily forced out of the ducts by gently stroking them 
with the handle of a smooth pencil or scalpel, and they were 
never seen to issue at more than one opening. So far, thin sec- 
tions of the oyster, as observed by the writer, have not shaken 
his belief in the accuracy of the observations of Lacaze-Duthiers. 
There is no evidence of the existence of three generative open- 
ings on either side of the animal, as asserted by Davaine, nor is 
it worth whileto more than notice Home’s error with regard to 
the water-chamber above the gills, which he regarded as the 
oviduct. 
At the time the oyster is full of spawn the generative organ 
completely envelops the viscera (liver, intestine and stomach), 
except a small portion at the anal end of the intestine and the 
head end of the visceral mass. All of the superficial ducts 
trend toward and join directly or indirectly the main duct on 
either side of the body, into which they pour their products as 
the latter are received from the immense number of follicles in 
which they are matured. We may repeat that at no time do we 
find the generative organs quite undeveloped ; if they are not 
