The Canadian Oyster. 3 53 



rudiment of the shell becomes visible. The first trace 

 is' a large pit called the shell-gland on the back of the 

 animal, mistaken by Brookes for the gut. This pit 

 flattens out and forms on the second day a saddle- 

 shaped area, at the sides of which two small calcareous 

 particles (Fig. 2) show the incipient shell. 



The shell grows larger day by day till on the sixth 

 day it half covers the animal. On this day, the last to 

 which the artificially beared larvae lived, the solid mass 

 of cells originating from division of the larger blas- 

 tonieres becomes hollowed out, and constitutes the 

 .stomach, and the mouth opening can be seeu. There 

 can also be seen behind the mouth on each side a little 

 hollow vessel with a vibrating sphere within it. These 

 are the otocysts, the so-called ears, which are found 

 throughout all Mollusca in the region of the foot. As 

 the Oyster has no foot they are not found in it when 

 adult, and it is an interesting fact here recorded, so far 

 as I am aware for the first time, that they are found in 

 the larvae. They are called ears, but their principal 

 function is not hearing, but keeping the animal in- 

 formed of its position with regard to the vertical, and so 

 enable it to balance itself. One is reminded of the fact 

 that the semi-circular canals in the human ear have a 

 similar function. Tlie later larvae which were cap-, 

 tured by the tow-net are characterised by possessing a 

 straight hinge to the shell totally unlike the hinge of 

 the adult. The front part of the animal can now be 

 completely withdrawn within the valves. The ridge of 

 skin bearing the powerful cilia, the prototroch, has 

 grown into a pair of lobes and is now termed the 

 " velum." It is suspected that the velum is later 

 transformed into the palps when the Oyster settles 

 down, but this so far as I know, has never been proved. 

 The beginnings of the liver, as two yellowish out- 

 growths from the sides of the stomach can be seen, and 

 also the intestine can be made out. 



A few words on the general situation of the Oyster 

 Fishery in Canada may now be in place. Abundant 

 oysters constitute one of the many gifts of Providence 

 which made Canada a desirable place to live in. 



