THE BRITISH COLUMBIAN OYSTER 133 



to have come in contact with sperms already — those that are in process 

 of segmentation are sure to have done so. This restricts the experiment 

 to finding specimens just before, but just on the point of, extruding eggs. 



I also tried Atlantic oyster eggs with Pacific oyster sperms, as well as 

 Atlantic oyster sperms with Pacific oyster eggs, but without success, 

 as might be expected. 



Comparison of Species. — I mounted eggs, embryos, and larvae of 

 both species together under the same coverslip for comparison — those 

 of the small British Columbian oyster looking like giants beside the 

 corresponding stages of the large Prince Edward Island oyster. 



For the study of segmentation the Atlantic oyster is of advantage on 

 account of the smaller size and greater transparency of the eggs. The 

 order of segmentation in the Pacific species appear to be the same as that 

 of the Atlantic, and to be subject to similar variations. I have found 

 in the mantle cavities of parent British Columbian oysters all stages from 

 the egg up to those stages in which their own minute shells were as large 

 as . 138 mm. in length. I have taken larvae in the plankton of which the 

 shells were as small as .165 mm., as well as different larger sizes. The 

 young must leave the protection of the parent somewhere between these 

 two sizes. They have a straight hinge-line of half the length of the shell, 

 and are of a general light complexion, with five or six dark blotches in 

 the regions of the liver and the velum. 



Some of the preceding statements come into conflict with what Prince 

 wrote in 1895. His paper states: 



"Under specially advantageous circumstances I have been enabled to carry on 

 investigations upon three distinct species of oyster, each distinguished by peculiarities 

 in breeding habits which are of the highest moment." 



These were the English, the Eastern Canadian, and the British 

 Columbian oysters. His original contributions refer to the last: 



"The two elements (eggs and sperms) are found in different individuals in our 

 Atlantic oyster. In other words the male oyster is distinct from the female. The 

 same holds true for the British Columbia oyster, as my researches last siimmer on the 



Pacific coast demonstrated for the first time The eggs were less than 



one-third the diameter of the English mollusc The number of 



males was greatly in excess of the females." 



The eggs examined must have been immature — taken from the ovary. 

 The great excess of males was doubtless due to the time at which they were 

 examined, but no mention of date or particular locality is made. Refer- 

 ence is made to Hoek's observation that a European oyster containing 

 eggs in the reproductive ducts was found to contain sperms two weeks 

 later, and was therefore female at one stage and male at another. The 

 statement that: 



" All investigators agree that nothing of this kind has been discovered in Atlantic 

 oysters," 



would not hold for the present day. Kellogg (1890) states: 



