SPAWNING AND SETTING OF OLYMPIA OYSTERS 
459 
is required for the maturation of the eggs. The data here described indicate that 
the ordinary marketable native oyster produces a brood of from 250,000 to 300,000 
larvae. 
Table 12 .—Number and stage of development of larvae in broods of IS oysters, and number of larvae 
in 2 groups of 6 broods each 
121 
125. 
126. 
127. 
128. 
129. 
130. 
131. 
132. 
139. 
140. 
141. 
142. 
Oyster specimen no. 
Length 
Width 
Number of 
larvae 
mm 
mm 
Stage 
32.7 
30.3 
28.0 
29.5 
29.0 
29.7 
31.0 
23.5 
28.2 
36.2 
29.2 
28.5 
36.8 
23.5 
24.0 
23.5 
27.5 
23.0 
21.2 
25.8 
19.2 
24.4 
26.2 
27.0 
23.3 
26.2 
130, 628 
113, 142 
95, 667 
150, 600 
156, 875 
184, 114 
355, 500 
69, 490 
126, 174 
293, 473 
213, 781 
136, 666 
171,818 
Morulae. 
Straight-hinge 160/1-170 /i. 
Do. 
Morulae. 
Do. 
Late morulae. 
Morulae. 
Straight-hinge 160/i-170/i. 
Do. 
Early gastrulae. 
Gastrulae. 
Do. 
Do. 
1 
2 . 
3 
4. 
5. 
6 . 
1 
2. 
3 
4. 
5. 
6 . 
Average. 
Average. 
Oyster Bay 
38.1 
40.6 
45.7 
38. 1 
40. 6 
45.7 
33.0 
30.5 
30. 5 
30.5 
33.0 
35.5 
Mud Bay 
283, 273 
38.1 
38.1 
38.1 
38.1 
43.2 
35.5 
30.5 
30.5 
33.0 
25.4 
25.4 
27.9 
247, 199 
It has been observed that most specimens carrying larvae appear to have dis- 
charged almost all of the eggs from the gonad, for the meats are generally transparent 
and watery. This is in contrast to Galtsoff’s (1930a) observation on Ostrea virginica 
that at a single spawning only a relatively small proportion of the eggs are discharged. 
The difference may be related to the fact that the native spawns alternately as male 
and female (Coe, 1931a, b). 
Stafford (1914) stated that the presence both in the parent and in the bay of all 
swimming stages shows “that the young do not all swarm out from the brood chamber 
of the mother at the same time, age, or size, but filter out gradually, perhaps during 
the gaping condition of the shell while respiration is going on in the parent.” In table 
12 the stage of development of the larvae of 13 broods is given. In proportion to the 
size of the parent there does not appear to be a significant difference in the number of 
larvae per brood with respect to stage of development, although it is true that the 
largest broods consist of embryos. While this evidence neither confirms nor refutes 
Stafford’s idea of the gradual release of the larvae, it is probable that many of the 
free-swimming larvae of small size found in plankton samples may be the result of 
abortions. Disturbing the parent oysters appears to cause them to discharge broods 
of “white larvae” or those which have not developed valves. In many cases oysters 
have been taken up from the beds and placed in dishes of clean running seawater in 
the laboratory, and those specimens bearing young larvae observed to discharge them 
by opening and closing the valves. That such abortions occur in nature is shown bv 
statistical sampling of the oysters on certain beds. 
