BULLETIN OF THE UNITED STATES FISH COMMISSION. 283 



The first collectors of the kind described were placed in position upon 

 the same day when the first spawn was poured into the pond. This oc- 

 curred on the 7th of July last. 



Other collectors were then put down at odd dates during the remain- 

 der of the month of July. The care of this portion of the experiment, 

 together with the spawning of the oysters themselves, was mostly in 

 the hands of Mr. H. H. Pierce, whose share in the work was, to say the 

 least, as important as my own. 



METHODS OF TAKING AND INTRODUCING THE SPAWN INTO THE POND. 



The oysters used for the purpose of spawning were taken from the 

 vicinity of the oyster-house, which stood only about twenty yards from 

 the pond, besides others which were obtained from the deeper waters 

 of the adjacent bay. It was found that the eggs of those from the shal- 

 low water near the pond were as readily fertilized as those from the 

 deeper water, and no difficulty was experienced at any time until to- 

 wards the latter part of July in obtaining an abundance of good spawn 

 for our experiments. 



The oysters from which spawn was obtained were carefully opened by 

 removing the right valve and allowing the soft parts of the animal to 

 remain attached by the muscle to the left one. The spawn itself was 

 then pressed out of the generative organs by means of a pipette gently 

 stroked over the gland and out along the course of the efferent ducts, 

 so as to force the spawn out into the upper gill chamber, as described 

 in previous publications by the writer. 



The sexes were distinguished apart very easily by what the writer has 

 described as the "drop test," which consists simply in dropping the 

 spawn from a pipette into a dish of clean sea-water and watching the 

 kind of cloud which it forms after it strikes the water. Invariably, if 

 the specimen was a female, the eggs would break up into a granular 

 cloud which could be very readily seen to be composed of very minute 

 whitish bodies if the transparent vessel was held up so as to look down 

 through it upon a dark ground below. 



In case the specimen was a male the drop of milt would not so readily 

 break up, but would exhibit a somewhat glairy consistency ; and if the 

 drop was stirred in the water it would break up into wisps and streaks, 

 so as to appear, on a small scale, like a series of minute mare's tail 

 clouds such as are seen in the sky at times. This test was found so 

 practicable that we were able to readily teach a novice how to distin- 

 guish the sexes apart in one lesson. 



The method of taking the spawn was just as easily learned by Mr. 

 Pierce and Mr. Shepard, both of whom soon became as expert as the 

 writer in the practice of the art of taking oyster spawn. The spawn 

 so taken was mixed together in a small dish. The milt and eggs placed 

 in contact at once were thoroughly stirred together and poured from 

 time to time, as the water became milky in the small glass collecting 



