No. 522] THE CANADIAN OYSTER 



361 



backwards and then down, finally passing- towards the 

 median plane to the anal opening over the adductor mus- 

 cle. The stomach sometimes contains diatoms and 

 desmid-like clusters of one to four nucleated cells. 



The nervous, circulatory, excretory and reproductive 

 systems remain undescribed, and shall not be treated of 

 in this paper; they bear less important relations to those 

 characters of external morphology and gross anatomy 

 that are so useful as marks of recognition and description. 



The first, second and third spat oysters caught on glass 

 were of different sizes and were consequently devoted to 

 morphology, but the fourth, being of approximately the 

 same size as the first, was used for a physiological ex- 

 periment in growth. This spat was procured on the 

 afternoon of August 31 at Ram Island, about six miles 

 from the station, and measured at 5 p.m. .861 X -953 mm. 

 in height and length and had about sixteen gill filaments. 

 It was kept under the bridge of Keir's wharf until the 

 afternoon of September 1 and measured again, but it 

 showed no increase of size. It was then taken to Ram 

 Island and placed under its original conditions in a 

 crock, and at 4 p.m., September 7, it measured 1.276 X 

 1.261 mm. and had about twenty-four gill filaments. It 

 was kept in running seawater until 5 p.m. of the eighth 

 and then put under the bridge of the wharf until the 

 morning of the ninth, when it was again taken to Ram 

 Island. It did not grow either in the running water or 

 under the bridge where there is at times considerable 

 tidal current. On the forenoon of the sixteenth it was 

 again brought in and measured 1.753 X 1.661 mm. From 

 these observations it would appear that the young spat 

 did not become immediately accommodated to new condi- 

 tions after being disturbed, that during a period of six 

 days of undisturbed growth it increased to one and one 

 half times its original height, and that at the end of seven 

 days more it had grown to twice its original height, One 

 might say that it doubled its height and length in two 

 weeks. 



