12 



temperature. The numbers of young oysters increase gradually 

 and reach their maximum from the second week in May to the 

 last week in June. After this, the numbers very gradually 

 decrease until, by the first of September, hardly any are to be 

 found. 



Towings, which have been the writer's chief means of de- 

 termining the spawning season are made with a net S'. .-en 

 inches in diameter composed of silk bolting cloth containing 

 150 meshes to the inch. This net is towed behind a boat. Where 

 records of tows were wanted to obtain a series, towings were 

 made as uniform as possible, that is, they were made from a small 

 power boat propelled by oars at a uniform rate and ext-nding 

 over a period of thirty minutes ; during this time the contents of 

 the net were emptied four times. Checks were run at times', to 

 see how nearly two towings would correspond. A second towing 

 being made immediately after the first, in the same locality. \'be 

 following are some of the results of the number of larvae ol)-- 

 tained at different times together with the checks: 1st., 90.000; 

 2nd., 130,000; 3d., 125,000; 4th, 82,000; 5th., 8,000; 6th, 2,500; 

 the checks were: 1st., 92,000; 2nd., 124,000; 3d., 124,000; 4th., 

 82,000; 5th., 9,200; 6th., 2,300. There is, of course, consider- 

 able difference in some cases, yet it must be remembered that 

 these results are estimated counts,- the total being determined 

 from the actual count of a certain proportion. Thus it is, that 

 differences will arise, even if a second estimate be made from 

 a second count of a single towing. On the whole, the num- 

 bers indicate that there cannot be very much difference in the 

 total number of larvae in the water, and that the towings rep- 

 resent tolerably uniform conditions. 



Since then, the larvae are found in greatest abundance dur- 

 ing May and June. It naturally follows that the greatest num- 

 ber of spat will settle during those months. Consequently clean 

 shells planted during those months will be most likely to gather 

 spat. Actually, however, there are enough young in the water 

 during April to be sure of a favorable set. Moreover, shells 

 planted in April are not apt to become fouled so soon as those 

 planted later in the season ; since the fouling growth reproduces 

 and increases more abundantly when the water is warmer. Al- 



