67 



completely, contained the largest number of young brood. We also found that the size of the 

 young depended, to a great extent, upon the depth of water. Those first detected by us were from 

 two millimeters to one centimeter in length, and as the shoal-water oysters spawn first, and as we 

 found the young of the largest size in shoal water, I infer that the attachment of the oyster occurs 

 very near the location of the parent. 



The hurdle in the Big Annemessex was subjected to four examinations. It was placed in 

 position on July 9, and on July 19, when the first examination was made, there were a few oysters 

 on the tiles, but so small that a microscope was necessary in order to recognize them. 



The second examination was on August 2, and the oysters were then quite perceptible and 

 easily counted. The total number of oysters on the tiles was then 1,506; deducting those on tile 

 No. 7, which tile was removed, there were 1,177. The number on a tile varied greatly, the max- 

 imum being 348 and the minimum 26. 



The third examination was on the 23d of August. The oysters had increased very much in 

 size and in numbers. The total number on the tiles was now 1,334, showing an increase of 0.13 

 per cent, of the number at the second examination. The number on the lower side of the tiles 

 was much larger than on the upper. A tile (No. 2) was removed, and, deducting the number of 

 oysters on it from the sum, there were 1,202 still on the hurdle. A few oysters were injured, prob- 

 ably by raising or lowering the hurdle from and to the bottom. 



The fourth examination was on the 10th of October. The total number of oysters was then 

 539, showing a decrease of 55 per cent. At this examination about two-thirds of the oysters were 

 of the third class, or over three-quarters of an inch in length, and two of them were over two 

 inches long, being thus of the second class. All, however, could be distinguished as of very recent 

 growth, being very long and thin, with thin, delicate shells, easily broken with the thumb-nail or 

 point of a penknife. The largest numbers were still found on the lower sides of the tiles. A 

 moderate number of oysters had been injured by rough handling. 



I infer from the four inspections made of this hurdle, and from the one or two made of others 

 before they were removed, that the first attachment of young began, as I have said, about the 

 middle of July, and continued until about the 20th of August, as on the 23d of that month there 

 was no indication of any recent attachment. Probably it reaches its maximum number about the 

 end of July, and decreases afterwards. The mortality after the 23d of August was very great, 

 fully 50 per cent, perishing from some unknown cause, which, though unknown, is certainly nat- 

 ural. We did not notice any evidence of the destructive effects of drills or other animals, though 

 their agency would only be discovered by the evidence of the holes in the upper valves, but as 

 those valves were never present, it cannot be said with certainty that the destruction was not due 

 to them. Whatever the cause, the fact is that 50 per cent, perished in the first six weeks of their 

 existence. 



The tiles have shown that the increase in size is much greater than was supposed, and are the 

 first and only authentic evidence upon that point which has been produced with regard to the 

 American oyster. Again, it is conclusively shown by these tiles and some others that were dredged 

 up from the Woman's Marsh beds (Hurdle No. 24), that the greatest attachment is on the lower con- 

 cave side, and consequently that whatever may be the movements of the embryo oyster before 

 attachment, during the period just prior to it they are near, if not on the bottom, and in seeking 

 their place of attachment they must rise. In this they are similar to the European variety. The 

 selection of the lower sides of the tiles and the interior of the "boxes" may be an effort of nature 

 to provide some protection for the young brood, by, to a certain extent, inducing them to seek 

 dark and secluded points for attachment, or the large number found in such places may be due to 

 the inability of the various enemies of the spat to get at them when thus protected. 



It is a matter of very great regret that we have not a large number of specimens and obser- 

 vations for comparison, as all the future investigations in this field would be greatly assisted by an 

 accurate knowledge of the rate of decrease in number and increase in size of the oysters, and it is 

 to be hoped that the hurdle in the Big Annemessex will be allowed to remain in position long- 

 enough to permit the meager, yet valuable, information it can produce to be made public. 



