[5] EXPERIMENTS IN OYSTER CULTURE RYDER. 767 



vivors now remaining, and if one is careful to examine the dSbris and 

 sediment at the bottom of the aquarium a few dead shells of embryos 

 may be detected with all of the soft parts gone. The most important 

 step in advance to-day has been a thorough test of the cotton-wool fil- ^ 

 ters, which will hold the eggs, but which will lodge in the meshes of the 

 filter, which is a serious drawback. This requires that after using one 

 of the filters for a short time, in order to change the water on oyster 

 embryos, its action must be reversed ; that is to say, one must let fresh 

 water pass through the contrary way in order to wash out those em- 

 bryos which have lodged in the meshes of the cotton wool. 



In consequence of the air-blast blowing continually over the surface 

 of the water in the hatching-dishes, there has been considerable evap- 

 oration going on, so as to raise the specific gravity of the water in the 

 dishes considerably. This does not seem to affect the health of the 

 oyster larvse which are still alive. 



I fertilized a lot of ova to-day, with very unsatisfactory results; the 

 impregnation was not at all successful. Ten adult oysters were used in 

 the operation — 3 males and 7 females. The males were plentier than 

 on previous days. Temperature of the water to-day ranged from 80° F. 

 to 85° F. 



June 14. — Cottonwool filter impracticable for use with a continuous 

 flow of water, but may be useful in the course of other experiments for 

 the renewal of the water on eggs and embryos. This was fully tested 

 by using a series of McDonald jars, connected together with rubber 

 hose somewhat like a series of Wolff's bottles. The exit-pipe of each 

 jar was filled with a cotton- wool filter, so that the water in the third and 

 last jar had undergone three distinct filtrations, the result of which was 

 that the water had become exceedingly clear and free from foreign i:>ar- 

 ticles, in fact had been more effectually cleansed than by the use of any 

 other filter I ever had seen tried. Theoretically this apparatus, through 

 which the water ran in a stream about as thick as a crow's quill, ought 

 to have retained the eggs and embryos of the oyster, even though 

 these were only one five-hundredth of an inch in diameter. The result 

 of an experimental test showed that such was the fact; that the eggs 

 and embryos would be retained, but that they would lodge in the meshes 

 of the filters, where they would finally be covered by other sedimentary 

 organic and inorganic matter. The result of this experiment showed us 

 clearly that this method of incubation would have to be abandoned for 

 something which would meet aud satisfy the conditions of our problem 

 more completely. A poor lot of ova were used in testing this apparatus, 

 and after its unfavorable performance was made apparent, it was not 

 thought advisable to waste any more eggs in its use. The prevailing 

 temperature of the water to-day was from 82° F. to 87'^ F. 



The embryos of previous lots which had been incubating in glass 

 dishes and aquaria had not been amounting to anything up to this time; 

 they were therefore abandoned after a few had reached the age of from 



