[11] EXPERIMENTS IN OYSTER CULTURE RYDER. 773 



of the fry which had been attached to the surface of the shells. We 

 could uot discover that it had increased perceptibly beyond the original 

 volume of the egg but could readily make out the course of the intes- 

 tine, the liver, and stomach, in the cavity of which we could perceive 

 the particles of food which had been swallowed in active rotary move- 

 ment, impelled to rotate within the alimentary cavity by the numerous 

 vibratiug cils or filaments with which its iuner surface is clothed. The 

 presence of a body cavity was very evident, but no evidence of a pulsatile 

 movement or the presence of a heart was evident. The hinge border 

 of the valves of these embryos was truncate and linear, as in the valves 

 of the embryos of the European ouster. No evidence of an umbonal 

 prominence with a spiral tendencj^ was apparent, such as may be per- 

 ceived in the valves of the larval shell when it is over four times as 

 large across, or of the size when it is suddenly converted into that of 

 the spat, as I have described elsewhere. • 



July 26. — I fertilized a very fine lot of eggs to-day at 10 a. m., which 

 began to swim about at 2.30 p. m. These were placed in apparatus. 

 No. 1, in which the old oyster shells had been introduced, as already de- 

 scribed. They may, however, be a little too numerous for the volume 

 of water, which we estimate in these latter experiments should equal 

 about 200 times the bulk of that in which the eggs were originally im- 

 pregnated. This dilution, we find, prevents the development of any 

 putrescent action, but does not arrest the development of hypotrichous 

 and peritrichous infusorians in vast numbers in all of our apparatus. 

 I am latterly inclined to regard the infusorians as a necessary evil not 

 to be gotten rid of. In fact, I doubt if they do any damage further thais 

 to act as scavengers. I often noticed, even when the water in our appa- 

 ratus was perfectly sweet, that the amoebse, infusorians, both stalked 

 and free-swimming species, vastly exceeded in numbers the oyster em- 

 bryos present in the incubating apparatus. 



I introduced a simple and effective floating collecting apparatus into» 

 the aquaria to day. I took some corks and cut into them some distance 

 with a knife, and then took slips of mica and pressed them into these 

 incisions edgewise in various positions. Having arranged my slips of 

 mica on the corks so that they could not be readily detached, the whole 

 was placed in the a;)aarium so that the plates of mica would be wholly 

 immersed. These were my collectors upon which the fry could attach 

 itself. When fixation had been accomplished it was an easy matter to 

 transfer these slips of mica, with the fry attached, to the stage of the 

 microscope for more critical and exact inspection. But, alas! my ex- 

 pectations were not realized; I did not succeed in having any embryos 

 attach themselves to the slips of mica in the course of further experi- 

 ments. Collectors of this kind were now introduced into both apparatus 

 No. 1 and No. 2. The temperature of the water today ranged from 83°' 

 to 90° F., a perceptible rise since the 22d and 23d. 



July 2,1. — I could find to-day but very few of the embryos which were 

 fertilized yesterday, and I sought in vain also for those of the 22d,which 



