PROGRESS IN BIOLOGICAL INQUIRIES, 1929 1115 



imported Japanese seed oysters. It lias been found that the Jap- 

 anese drill occurs in restricted areas, while the eastern di-ill is more 

 generally distributed; up to date it has not affected the principal cen- 

 ters of oyster production. About 20 other species of Jaj)anese forms 

 have been introduced in Puget Sound and many of them thrive, be- 

 coming potential sources of danger. 



PHYSIOLOGY OF ADULT AND LARVAL OYSTERS 



Temperature effect an feeding of Gulf coast and Japanese oysters. — 

 Dr. P. S. Galtsoff continued a study of the physiology of feeding and 

 spawning of oysters. Several experiments on the effect of temper- 

 ature on the rate of feeding were carried out in April at the tem- 

 porary laboratory established at Offats Bayou, near Galveston, Tex. 

 It has been found that similar to the behavior of oysters from Cape 

 Cod and Long Island Sound, the oysters from the vicinity of Galveston 

 Bay respond to the changes in temperature in the same manner as 

 those growing in the northern w^aters. The rate of feeding increases 

 with the increase of temperature, reaching the maximum at about 

 30° C. (86° F.) Cessation of feeding occurs at the temperature be- 

 tween 7° and 9.5° C. (45° and 49° F.) ; that is, at the same tempera- 

 ture which causes the cessation of feeding in northern oysters. The 

 conclusion seems inevitable that the warm waters of the Gulf of 

 Mexico fail to produce any physiological changes in the ciliary 

 mechanism of the gills. A study of the effect of temperature on the 

 feeding of Olympia (Wash.) oysters {Ostrea liirkla) and the Jap- 

 anese oyster (Ostrea gigas) was made at the Jacques Loeb laboratory 

 of Hopkins Marine Station, Pacific Grove, Calif. The maximum 

 rate of feeding of the Japanese oyster (4 liters, or approximately 1 

 gallon, per hour) occurs at the temperature of 25° C. (77° F.) ; the 

 optimum temperature for feeding of the Olympia oyster is between 

 25° and 30° C. The highest rate of feeding of the Olympia oyster 

 is between 500 and 600 cubic centimeters (approximately 1 to 1^ 

 pints) per hour. Japanese oysters cease feeding at the temperature 

 of 6° to 7*' C. (43° to 45° F.) ; Olympia oysters stop feeding at the 

 temperature of 8° to 10° C. (46° to 50° F.). 



Factors wJiich affect spawning. — A study of spawning of oysters has 

 been continued and experimental work was carried out at Woods 

 Hole, Mass.. Galveston, Tex., and Pacific Grove, Calif. The experi- 

 ments were undertaken for the purpose of determining the factors 

 which control the discharge of the sex products of the female and 

 male oj^sters. The results obtained during last year confirm the con- 

 clusions previously reached and reported in the annual reports for 

 1927 and 1928, and add some new" facts which were unnoticed in pre- 

 vious experiments. It has been observed during the experiments 

 at Woods Hole that the spawning of male oysters can be stimulated 

 not only by the addition of eggs or egg water, but also by the addi- 

 tion of the sperm. In the latter case, the latent period of the re- 

 action — that IS, time elapsed between the addition of sperm and the 

 beginning of the reaction — is about 10 minutes, the same duration 

 as in the case of stimulation of the female by sperm. Since the 

 active principle of the sperm suspension does not pass through collo- 



