132 COMMISSION OF CONSERVATION 



this species, but I believe they are smaller than those of the Atlantic 

 oyster, which may have some relation to the particular mode of fertilization, 

 such as being introduced by the respiratory current, for fertilization must 

 take place in the mantle cavity. In some parts of the gonad ova may be 

 plentiful, while at other places there are only sperm-balls. Later, in the 

 warmer weather, the sperm may be pretty well run off and the reproductive 

 organ contain mostly eggs. In this way the younger oysters, and the 

 older oysters at the beginning of the season, may be physiologically 

 males, while older oysters at the height of the breeding season may be 

 physiologically females. 



Specimens from Hammond bay showed the same phenomena. After 

 finding an abundance of the larger and more normally occurring oysters 

 at Nanoose bay, I decided to make a more extensive examination to 

 determine if there were more than one species, or if the first found speci- 

 mens under stones were the same as those exposed on the surface of gravel, 

 sand, or mud flats, and I brought home a pail-full of picked specimens 

 to keep as a convenient stock from which to select and study at leisure. 

 In making measurements it is important to use only ripe eggs, that are 

 freed from each other and flow easily, and to select those that are spherical 

 or nearly so and not flattened by the weight of the coverslip, as well as 

 to extend the measurement to many oysters in order to exclude all possi- 

 bility of mistakes. On July 16 one of the specimens contained about half 

 a tea-spoonful of eggs in various stages of segmentation, lying free in the 

 lower valve — a mass of white granules. Ripe eggs ooze from the oviduct 

 into the branchial cavity, between the two folds of the mantle, where 

 they are retained next to the gills and without any retaining, sticky matrix. 

 It must be here that they first meet with ripe sperms from other individuals, 

 for before this the sperms of the same individual have been ripened and 

 discharged. At this time the whole oyster appears exhausted — the gills 

 rent, the flesh collapsed, emaciated, soft and discoloured, as if under- 

 going decomposition. On July 24, I opened one hundred of the stock 

 supply, and found only six with eggs, embryos, or conchiferous young 

 in the branchial cavity. All the others were in process of sperma- 

 togenesis and oogenesis. 



Artificial Fertilization. — An experiment that has often suggested 

 itself to me is to do the same with the common European oyster by way 

 of artificial fertilization as Brooks did with the Atlantic oyster of America. 

 Now that I had a species essentially the same as the European, I tried 

 it, and apparently with success. I separated out a mass of ripe eggs from 

 the body of one individual, and a mass of -motile sperms from another, 

 and mixed the two masses. There developed embryos from the mixture. 

 Of course it is difficult to be sure that sperms had not already had access 

 to some of the riper eggs, while in the oviduct. Unripe eggs are of no use; 

 eggs freed from the gonad and lying in the mantle cavity are very likely 



