THE OYSTER-INDUSTRY. 215 



Such is the scicutific history of the oyster-embryo. The practical utility of the knowledge, however, to the 

 most of us, is that the Americau oyster lays a vast number of eggs, but that they are exposed to dangers so 

 constant and innumerable, that under ordinary coiulitious few ever come to life, or at any rate succeed in living 

 Ion"' enough to anchor themselves and take on the protection of shells. This is ouly another example of a fact well 

 known to naturalists, and occurring widely among animals of low grade. The number of eggs laid, or even of 

 individuals born, luis very little to do with the abundance of a species, which is "determined, mainly, by the 

 external conditions to which it is exposed". 



Life of the young oysteii. — The young American oyster leads a peculiarly precarious time, since it is 

 first thrown out an unfertilized egg, and the chance that it will immediately meet with a male cell nuist be very 

 slight; yet if it does not it will perish, for the sea-water destroys unimpreguated eggs within a few minutes after 

 contact with it. Having by good chance become fertilized by meeting a male cell, the next period of great danger 

 is the short time during which the embryos swarm to the surface of the water. They are so perfectly defenseless, 

 aiul so crowded together close to the surface, that a small iish, swimming along with open mouth, might easily 

 swallow, in a few mouthfuls, a number equal to a year's catch. They are also exposed to the weather, and Dr. 

 Brooks found that a sudden cold wind or fall in temperature, as occurred several times during his experiments, 

 killed every embryo in his care. The number whiith are destroyed by cold rains and wiiuls must be very great 

 indeed. As soon as they are safely past this stage and scatter and swim at various depths, their risks from 

 accidents and enemies are greatly diminished. Up to this point, which is reached in from twenty-four hours to 

 six days, there is no difficulty in rearing them in an aquarium, provided uniform warm temperature be preserved. 

 "Mobius,"ac(!ordiug to Brooks, "has estimated the luimber of adults which spawn each year, and multiplying this 

 number by the average number of eggs laid by each, and dividing by the number which grow up, he reaches the 

 conclusion that each oyster which is born has i,Tr5;ooo of a chance of reaching maturity. In the case of the 

 American oyster the number of eggs is very nuich greater and each one's chance of survival is accordingly very 

 much less, and it is evident that the great fertility of the oyster will not protect a bed from destruction by 

 excessive dredging." 



In all these early stages, both as egg and as larva, the young swimming oyster is designated popularly as a 

 "spat", "spawn", or "set". Perhaps s^iawn is the best of these terms to be used for our purpose, covering the 

 time from the discharge of the egg until the oyster has attached himself and appears with shells, as a visible speck 

 upon the shell or other anchorage which he has chosen. From this time until he distinctly shows the double 

 bivalcxht)- character of his shells and is an oyster, the infant is usually spoken of most expressively as a "blister". 



Distributions of spawn by wind and tide. — Eegarding now only the vicissitudes of wind and weather, 

 how far will the spawn drift from the parent, under favorable conditions, before it is destroyed, or else sink down 

 and attach itself? This is one of the subjects in respect to which we have small accurate information, and about 

 which there is necessarily much mystery. A few years ago it was accepted as true, that masses of spat were 

 drifting back and forth with the tides and currents all around the coast, and it was only deemed needful to place 

 something on the bottom for this spat to attach itself to, in order to catch a full "set" and obtain thousands of 

 bushels of young oysters. In case of failure, the currents were blamed in an indefinite way for not bringing spawn 

 to the beds. We have seen, though, how delicate and sensitive to harm Dr. Brooks ascertained the young oyster 

 to be, and furthermore, that, even after the vivifying influence of fertilization, it would float only a few hours before 

 becoming ready to attach itself to some support. Now, under ordinary circumstances, the summer drift of tidal 

 currents does not exceed half a mile to a mile an hour, and there would, therefore, not be time for the spat to be 

 carried a very long distance before its turn. If the aid of a strong wind is called in, it must be remembered that 

 any harsh breeze would kill the spawn. 



Observation has shown, moreover, in many cases, that a district contiguous to an existing bed of natural or 

 transplanted ousters caught a set, while another area not far away did not, the opposite being never true. When 

 a region — at least everywhere outside of Chesapeake bay — has become depleted of its natural growth of oysters, it 

 is extremely rare that any spawn ever catches there, though on each side close by and in the line of direct currents, 

 there may be productive tracts; by "close by ", I mean within two or three miles. Such an instance is found in 

 Warren river, Ehode Island, where there has not been a "set" for ten years. Men there will explain that it is only 

 once in several years that "the right combination of temperature and degree of saltness in the water happens at 

 the moment when the spawn comes in", but it is evident that formerly a growth of young oysters occurred regularly 

 every season, and no "combination" was required. The simple truth is, that there are now no parent oysters native 

 to Warren river, or acclimated in it, to furnish spawn, which does not now drift in from the outer bay. Practical 

 men, therefore, in phmuing their work, put little trust in fickle currents and the feeble vitality of drifting sjiawii, 

 Avhilo some deny wholly that it drifts at all. One of these latter theorists — and the view is too extreme, I haAC no 

 doubt— who lives at Providence, Rhode Island, showed me at his wharf in the Seekonk river a float containing a 

 hundred bushels of oysters. The tide was running beneath it and beside it with great force, as, evidently, it always 

 does at that spot. On the 1st of August, 1877, he had that float filled, as now, with native oysters that he had 

 brought from this bed. Suddenly he saw one shoot out a milky substance. "There's an oyster spawning," he 

 cried out, and called his son to witness it. In an instant another exuded the spawn, shot it far out, and then, 



