[13J ARTIFICIAL PROPAGATION OF OYSTERS. 753 



So far as the current acts in keeping the eggs in motion and free 

 from contact, it is beneficial; but this can be accomplished in other 

 Vinys, and in future experiments I should throw the action of currents 

 out of consideration. 



Aeration. — In the early part of the season this was deemed a very 

 important matter, and though our exj)erience failed to confirm the 

 opinion, yet notwithstanding, I am inclined to think that in the future 

 it will be demonstrated that the influence of aeration is considerable, 

 and that it is a necessary factor to success. Certainly the immense 

 numbers of embryos, amounting to many millions in the aquarium jars, 

 cannot, in so confined a si)ace, receive the normal quantity of oxygen, 

 and the fact that constant aeration has been found necessary in all an- 

 alogous systems of artificial culture makes it probable that it is essen- 

 tial to successful oyster propagation. But, notwithstanding this appar- 

 ent necessity, my actual experiments, both at Beaufort and Fair Haven, 

 did not appear to be influenced advantageously by artificial aeration, 

 though I gave it a long trial, under various conditions, before abandon- 

 ing it. Air was forced through the water in large and small bubbles, 

 at the bottom, in the middle, and just below the surface of the water 

 in the jars; the jet was constant at one time, then changed to an inter- 

 mittent one, and jets were forced over the surface of the water in the 

 jars or shallow dishes; but in no case with any marked advantage. As 

 I have stated in referring to the influence of other conditions, the em- 

 bryos that were undisturbed advanced most rapidly, and lived longest. 

 As, however, other investigators may wish to experiment in this direction, 

 and as the matter is not conclusively settled in my own mind, I append 

 sketches and descriptions of two forms of air-pumj), used by Brooks 

 and myself, which, as the apparatus is easily and cheaply contrived, 

 may be of assistance. In connection with the aeration of the water one 

 point of importance must be noticed, though I have alluded to it already 

 indirectly. The temperature of the air must be, as nearly as possible, 

 that of the water in the jars or plates. This precaution must be observed, 

 even if it is not deemed necessary to the life of the embryo, in order 

 that exact knowledge regarding the effect of aeration may be obtained. 



Effect of adding large amounts of lime to the icater. — Carbonate of 

 lime is the most important constituent of the shell of an oyster and the 

 probable necessity of increasing the amount available for the formation 

 of the shells of the embryos, early suggested itself to Brooks and my- 

 self. Before my arrival at Beaufort Dr. Brooks had made several ex- 

 periments in supiilying inordinate amounts of this constituent with 

 gratifying success; and in the majority of the experiments at Beaufort 

 we attempted to increase the amount by depositing in the bottom of 

 the jars or plates, fragments of the shells of oysters and one of the va- 

 rieties of echinoidea. The latter is known commonly as the " sand dol- 

 lar" and being flat, smooth and clean answered the purpose very well. 



Dr. Brooks succeeded several times in obtaining embryos in quite an 

 S. Mis. 46 48 



