SPAWNING AND SETTING OF OLYMPIA OYSTERS 
457 
mation on the mode of reproduction in this species was published. Coe studied in 
detail the spermatogenesis and life history of this oyster near La Jolla, Calif., and 
found it to be protandric. He stated that germ cells mature in the 1-year-old oyster 
and that at first the individual is male. During the rest of its life it is alternately 
female and male, although at any one time germ cells of both sexes may be found in 
the gonad because seldom are all of the sexual products discharged before the next 
phase begins. 
Stafford (1915) stated that spawning involves the discharge of eggs or sperm 
balls from the gonad into the suprabranchial or cloaca! chamber from which they 
reach the mantle chamber. He described this activity as follows: 
Eggs and sperms are liberated from the gonaducts into the suprabranchial chamber, and make 
their way through the water-tubes and gill-slits to the branchial chamber, which also serves as a 
brood chamber. In doing this they are assisted by the pressure of their mass * * *. Sections 
of oysters at the spawning season show eggs in the cavities of the gills. They do not pass readily 
through the gill-slits on account of the narrowness of the latter, but with the increasing mass and 
pressure the gills become stretched and the slits enlarged, and besides the gills appear in places to 
suffer disintegration. 
This explanation is obviously inadequate, for one has difficulty in understanding 
how the small increase in pressure due to eggs would force them through the gill 
apertures. Also, it is clear that considerable coordination would be required to keep 
the cloaca! chamber completely closed and prevent direct escape of the eggs. Galtsoff 
(unpublished manuscript) studied spawning in Ostrea virginica and reached the more 
probable conclusion that suction, created by opening of the valves during spawning, 
draws the eggs through the small openings in the gills. Elsey (1935) found that the 
openings, or ostia, in the gills of 0. lurida and 0. gigas have a diameter proportional to 
that of the eggs. The eggs of the former are about twice as great in diameter as 
those of the latter, and the ostia are about one-third larger. 
As has been described by Nelson (1922), Galtsoff (1930b, 1932) and others, eggs 
are finally discharged from the mantle chamber in Ostreavirginica but sperms are washed 
out through the cloaca with the water pumped by the gills. Stafford considered that 
in the native oyster the sperms also pass through the gills as do the eggs. While 
Stafford may have actually observed the discharge of sperms in this manner, the 
writer has frequently seen them issuing from the cloaca as in other species. At the 
time of spawning the sperms of 0. lurida are in clusters, or balls, made up of from 250 
to 2,000 or more sperms, according to the estimate of Coe (1931b), who stated further 
that in contact with sea water the matrix in which the sperms are imbedded disinte- 
grates, permitting them to swim free. Both Stafford and Coe considered that eggs 
are fertilized by sperms brought into the branchial chamber where the eggs are held, 
with the water pumped by the gills. Stafford thought self-fertilization might occur, 
though according to Coe’s interpretation this is unlikely. It is uncertain whether the 
sperms from one individual will stimulate spawning in functionally female specimens, 
as described by Galtsoff (1930b, 1932) for other species, though such is probable. 
The eggs are held in the anterior end of the mantle or branchial chamber adjacent 
to the gills and labial palps. Here they develop for a considerable period. It is 
remarkable that they are not swept out along the “waste canals” in the walls of the 
mantle which normally function to eliminate particles of silt and other rejected 
material. Stafford (1914) estimated that in British Columbia the period of develop- 
ment within the maternal “brood chamber” is about 16% days, while Coe (1931a) 
suggested “a period of approximately 10 to 12 days, perhaps” in southern California. 
Stafford’s work on this species is published in a series of six papers (1913, 1914, 1915, 
1916, 1917, 1918) some of which are frequently referred to below. 
