74 



oysters may spawn each year, but the attachment of the young is a very different thing, and 

 as the most precarious period in the life of the oyster is that -just anterior to its attachment, a 

 series of causes detrimental to the life of the embryo, while it is in its free swimming state, may 

 readily occur, and thus prevent such attachment. My investigation of the past season has proved 

 conclusively that the class of oysters termed "young growth" in my previous report were not of 

 the brood of 1878 but of 1877 or 1876. The character of the young found in both seasons, the 

 determination of the time of earliest attachment, and the growth and appearance of the oysters 

 on the tiles, have led me to this conclusion. As the young do not attach before the middle of 

 August, they could hardly reach such a size and shape by October as would prevent their recog- 

 nition as of the same season's growth. From the inspection of the oysters taken during the last 

 season, many being found with the generative matter unexpelled, I am of the opinion that a com- 

 bination of natural causes may prevent the expulsion of both the male and female cells, and there 

 would consequently be no impregnation during that season. As I mentioned in the report of 1878, 

 many persons of experience are of that opinion, and I now concur with them in thinking that not 

 only the attachment of young may not be general nor occur each year, but that the emission of the 

 products of generation may also be frequently confined to partial areas, and that by a combination 

 of circumstances there can be a total failure of impregnation on all beds of any locality. 



I also find by additional experience, that the yo*ng oyster is not fit for marketable purposes 

 until at least a year and a half or two years old, and consequently the total number of young 

 removed, as estimated in my previous report, would be a total sacrifice, and, as will be seen by 

 the table showing the number of oysters removed, this sacrifice probably amounted in 1878 to 

 148,800,000 oysters. 



By reference to the tables showing the success or failure of the several spatting seasons, it will 

 be seen that there is little or no regularity of either success or failure, but as we have only been 

 able to investigate the spatting of three seasons, it may be found by subsequent observations that 

 two similar seasons of success, moderate success, or failure, will follow each other; but so far this 

 has not been the case and in the period of three years we have, comparatively to the other seasons, 

 one at least of successful attachment. I can see no reason for supposing that there is any regular 

 recurrence of the spatting seasons, and am inclined to believe that the success or failure is due to 

 two causes: variations of temperature and variations of density; but I had no means of ascer- 

 taining the changes either of temperature or density in the years preceding those in which I have 

 been engaged upon this investigation, and in both seasons I arrived in the Sounds too late for the 

 temperatures or determinations of density obtained by the party to be, with reference to the spat- 

 ting, of practical value. 



Oysters will and do live in very dissimilar temperatures and in waters of very different densi- 

 ties, as is shown by their existence in the waters of North America from Nova Scotia to the Gulf, 

 and on both Atlantic and Pacific coasts. That the mature oyster is a hardy animal, readily adapt- 

 ing itself to new conditions and environment, is shown by the ease with which it is transplanted 

 from the warm waters of the Chesapeake to the colder ones of New England; from the dense and 

 salt waters of the ocean and bay to the brackish waters of the creeks and rivers or vice versa, 

 and from soft bottoms to hard or the reverse; but, naturally, this hardiness is not a quality of the 

 immature oysters or the swimming embryos. 



The influence of increased or diminished temperature upon the formation of the ova and sperma- 

 tozoa must be very serious, and, judging by analogy, it would seem probable that the formation 

 would be more rapid during a warm spring than during a cold one. Whether the formation has 

 been late or early when once formed, a sudden change of density or of temperature may so affect the 

 oyster or the generative matter that the latter would not be expelled. Only upon this hypothesis 

 can be explained the retention of the products of generation noticed in so many oysters, and which 

 is said to be so common, for none of the other conditions are subject to violent changes, such being 

 peculiar to the density and temperature alone. 



Professor Brooks states that he found both ova and spermatozoa ripe and fit fur fertilization 

 about the middle of May, and as the oysters were taken from shoal water, probably one fathom 

 deep, the shoal- water oysters were probably spawning throughout June. Both Professor Brooks 

 and myself found the ripeness of the oysters to depend upon the depth of water from which* they 



