RESUME OF THE STAGES OF DEVELOPMENT 81 



pailful of water showed 40 larvae. On the 8th a pailful yielded 63. On 

 the 10th a pailful gave 24, etc. These proportions appear to me to be 

 high, but I have no doubt that the places from which the water was taken 

 (near Barnegat and Tuckerton, New Jersey) are in a very rich oyster 

 region. 



The earliest in the season at which I have obtained oyster larvae from 

 the water was June 26, 1905, at Malpeque. They were 14, 15, and 16 

 units in length and not plentiful, although the larvae of mussels and clams 

 were. On July 11, 1904, oyster larvae were plentiful at the same place 

 and varied from 12 to 20 in length. In 1909 I planned extensive obser- 

 vations, and in order not to miss anything spread them over a large number 

 of oyster areas down the east coast of New Brunswick and around Prince 

 Edward Island. Judging the time from my experience of 1905, I began 

 taking plankton on June 25th at Caraquet and found that I was well ahead 

 of the season, as there were only a very few mussel and clam larvae in the 

 water, and these can always be counted on as first to put in an appearance. 

 The season proved to be cold and backward and the first oyster larvae 

 appeared at Cocagne on July 22nd. They were small, varying from 10 to 

 14 in length, and few, and were mixed with the larvae of mussels, quahaugs, 

 scallops, and one or two other bivalves. 



The number of oyster larvae, as viewed for a single season, begins with 

 a minimum, rises to a maximum, which is held for a period, and then falls 

 to a minimum again. The same is true for each bay considered as a whole, 

 although one bay may be a few days in advance of another. It is also 

 true for each oyster locality in a bay, even though one of these precedes 

 another in time. In each locality, such as the region about an oyster bed, 

 the first larvae, to appear are small and pretty uniform in size. Succeeding 

 catches will soon show a mixture of larger and smaller individuals because 

 the first will have grown while the fresh ones are coming on. Daily ex- 

 amination of plankton collections will keep the observer informed as to the 

 progress of the largest larvae until they reach their full size (55 units) and 

 at the same time the relative proportions in numbers of these older larvae 

 to the younger swarms with which they are associated. He can also 

 estimate approximately the age of the oldest ones, the length of time be- 

 fore those of any particular size will be of the same age, and at what time 

 there will be the greatest number of full-grown larvae in the water. As 

 this time approaches he will be in a position to judge if there are better 

 prospects arising. In a bay of some size there may be several such oyster 

 areas and then the conditions become more complicated. The larvae from 

 one may be carried over into another by the ebb and flow of the tide. This 

 may in places be a simple oscillation which carries the water back and for- 

 wards without mixing it to any great extent; but in some cases there 

 result tidal currents which draw water from different directions, mix it, 

 and carry it to a considerable distance, never returning it to the same place. 



qo?>io 



