766 EEPORT OF COMMISSIONER OF FISH AND FISHERIES. [4] 



July 12. — Eggs of the lOth, at 9 a. m. to-day, so diminislied in num- 

 bers as to be bard to find. Those still alive have velum developed and 

 are swimming about actively. Infusoria are developing rapidly and in 

 large numbers; of these there were large numbers of holotrichous spe- 

 cies, besides very small monads, which were by far the most numerous. 

 I have about concluded that we put entirely too many eggs into a given 

 volume of water, thus increasing the chances of putrefaction. I do not 

 see, however, that the protozoa are destructive ; none that I have seen 

 appear to be capable of destroying an oyster embryo. Some vibrios 

 which have made their appearance indicate a more alarming condition 

 of affairs. Eggs of the 10th were practically dead to-day, though a few 

 embryos might still be found after much searching. 



Eggs of the 11th were not as completely freed from milt as they 

 should have been. The water in the hatching-dishes is putrescent 

 this morning, with teeming hosts of putrefactive organisms. Zoogloear 

 membranes or pellicles are visible on some of the dishes. Heat has been 

 greater to-day than yesterday ; last night was cooler than previous one. 

 Thermometer 85° in the air at 9 a. m. ; water in the dishes 840 at the 

 same hour. Quite a number of embryos arc still alive however 5 the 

 last lot more developed than the first at the same relative age. Many 

 with the shell-gland developing. Some were also seen to disintegrate 

 while under observation. Some had a slimy filament attached to them 

 which impeded their progress in swimming. These phenomena may 

 explain Davaine's statement regarding the detachment of the velum; 

 in other words what he saw was probably simply a putrefactive process 

 involving the incipient disorganization of the embryos. 



At 2 p. m. I transferred the embryos of the 11th into a 2-gallon glass 

 aquarium, and then filtered off most of the water through a cotton-wool 

 filter, which seemed to work pretty well, separating the most of the eggs 

 from the water which runs through quite rapidly. The putrescent odor 

 after this operation was not now so apparent. 



The cotton-wool filter was constructed precisely as the one in which 

 filtering paper was used, only instead of the latter I used a thick pad 

 of raw cotton saturated with water, varying from one-fourth to three- 

 eighths of an inch in thickness.- This contrivance, for the construction 

 of which I had received my first hint from the experiments of Pasteur 

 and Tyndall, allows the water to pass through rapidly, but is very ef- 

 fective for a long time, as it clogs very slowly. I have great hopes of 

 the performances of this last form of filter. 



Meanwhile the putrescent action in the aquarium has apparently ex- 

 hausted itself. I have had the air-blast blowing on the surface of the 

 water, and have also immersed one blast-nozzle so as to cause the air 

 to bubble up through the water in the aquarium. 



July 13. — Putrescence has been to some extent impeded by the air- 

 blast, eggs of the 10th July swimming about at a lively rate and in the 

 condition of Brooks's Fig. 38. There are, however, but very few sur- 



