6 COMMISSION OF CONSERVATION 



position that it becomes difficult and unsatisfactory to make a comparison 

 with the shell of the free-swimming larva. The very youngest spats, 

 that have only a narrow rim of new shell (dissoconch) added to that of the 

 larva (prodissoconch), are likely to be free from any such modification, 

 but I could not find any young enough. The smallest oyster shells I 

 could find at the time were about the size of a man's thumb-nail, which 

 was far too large. 



Being blocked in this direction, I next resorted to experiment by put- 

 ting out bundles of brush tied down or weighted down with stones at likely 

 places for the capture of oyster-spat, and I also recalled the method of 

 putting out glass I had read about while studying the clam at St. Andrews 

 three or four years before. Strips of window-panes were stood in crocks, 

 in favourable places under the water, and looked at every day, each speck 

 that remained after rinsing the glass in sea-water being examined with a 

 lens and, if need be, with a microscope. 



In this manner, in due time, I caught a young spat, so close after its 

 fixation that there was little change in appearance — its identity with one 

 of my series of free-swimming larvse being unmistakable. This was the 

 supreme moment that knit all isolated observations into one fabric and 

 turned guesses into facts. The peculiar larva already mentioned was an 

 oyster larva, and this was an oyster spat, and, moreover, the present was 

 the period when the developing oyster changes both its habits and its 

 structure. Plankton had been collected since the first week in July; the 

 oyster larva had been under suspicion since the 25th of July; and now the 

 first oyster spat was captured on the 16th of August. 



There remained but to verify and fill in details. Spat increased in 

 numbers and size and were soon to be found on shells and stones, while 

 on the contrary the larvee became less plentiful and dwindled out early 

 in September. 



In 1905 I had the opportunity of studying plankton at Malpeque be- 

 tween the 7th and the 26th of June, and was unable to find any oyster 

 larvae, so that, putting this along with my previous observations, I felt 

 justified in concluding that July was the month for larvae and August the 

 month for spat. This and the following summer were spent in Gaspe, 

 Que., the next at Seven Islands, Que., and another back at St. Andrews, 

 N.B., so that I had no further opportunity to verify or extend my ob- 

 servations on the oyster until the summer of 1909, which was devoted to 

 the oyster and quahaug areas of eastern New Brunswick and Prince Ed- 

 ward Island. 



In the meantime I had learned to recognize the larvae of the silver- 

 shell (Anomia), the scallop (Pecten), and the clam (Mya), and had de- 

 veloped accurate methods of measurement and comparison. It being 

 unsafe to rely on sight and memory, I kept records of outlines of larvae 

 made with a drawing apparatus attached to my microscope, and of measure- 



