752 KEPORT OF COMMISSIONER' OF FISH AND FISHERIES. [12] 



tozoa hastened, but the animal becomes diseased, or at least abnormally 

 replete, from the absorption of an inordinate amount of food or the en- 

 dosmotic action of the fresh water. 



In experimenting at Beaufort I used for the impregnated eggs, while 

 segmenting, ordinary sea water, and in other cases water diluted one 

 third with fresh well-water, and met with sufficient success with the lat- 

 ter to impress rae with the peculiarity. In one case I divided the lot of eggs 

 immeditely after impregnation, subjected one half to salt water undiluted 

 and the other half to water diluted one-third, and noticed quite a marked 

 difference in the development of eggs and embryos, those in the brack- 

 ish water advancing most favorably and living longest ; but as I was not 

 able to continue these experiments in a very accurate manner, and as 

 so many other conditions may have influenced the development, it would 

 be rash to decide that a marked reduction of density is necessary to 

 the success of the experiments. On the whole, other things being equal, 

 I should prefer brackish water to pure sea water. It is worthy of note 

 in this connection, that at Fair Haven the exi)eriment failed at an early 

 stage when water from the Sound, which api)roximates to pure sea water, 

 was used; but as changes of temperature and errors of selection and 

 manipulation were accompanying causes of failure, the influence of the 

 density of tbe water remains obscure. 



As to the influence of the density upon the embryo, I am unable to 

 speak with any authority, owing to the fact that we had swimming em- 

 bryos under observation for but very short periods, and having in view 

 a particular end to reach, were loth to experiment with those that pro- 

 gressed favorably. Both Dr. Brooks and myself succeeded in raising 

 the embryo to an advanced stage in both salt and brackish water; but 

 we did not experiment with the water after once placing the embryos 

 in it, and consequently I am unable to say what would be the effect of 

 a change of density. The embryos are of so delicate an organization 

 that it seems probable that a change in this or in any particular must 

 affect them disadvantageously. 



Currents. — Oysters do not live, obviously cannot live, for any length 

 of time in perfectly quiet water. The currents passing over the beds 

 are necessary to the animals in many ways, but principally in supply- 

 ing food and in securing the contact of male and female fluids. It is 

 well known among oystermen that there is but a limited reproduction 

 on beds not subjected to the influence of tidal or other currents; and in 

 consideration of that fact I made a few experiments with the Intention 

 of ascertaining whether a current had any effect upon reproduction 

 other than the obvious one of securing contact of the generative fluids. 

 I accomplished my end and secured an artificial current, by revolving 

 in the aquarium jar a paddle wheel, composed of oyster shells, but the 

 api)liance had no appreciable effect except a deleterious one, and was 

 soon abandoned. Beyond securing more thorough aeration of the water, 

 currents in the aquaria appear to be useless; indeed, the more quiet the 

 embryos were, apparently the more successful was the experiment. 



