ZOOLOGY. 593 



spawn is used, mobile embryos will be produced. The spawning takes 

 place in 0. angulata for several weeks and gradually. 



"An inclosure about thirty- five feet square was prepared at Verdon, 

 into which the animated products of successive fecundations were 

 pouved. The sea water was permitted to enter this space through a 

 bed of fine sand, and to pass out in the same way. This epabled the 

 exi^erimenter to retain the artificially spawned embryos within the in- 

 closure. After a month of reiterated experiments our endeavors were 

 crowned with success. We had the satisfaction of finding some brood 

 fixed on each of the tiles placed in our experimental 'clear.' This is so 

 much the more remarkable as until last week [this ai)pears to have 

 been in July] no spat had yet attached itself to the numerous collectors 

 immersed on the oyster beds of the Gironde; that is to say, in the very 

 center of the clear." 



Mr. Ryder, commenting on these experiments, justly claims that they 

 are of the highest interest and may be of great practical value, especially 

 the means resorted to in order to prevent the escape and loss of the 

 embryos from the clear or pond. The Virginian oyster is related physio- 

 logically as well as mori>hologically to the Portuguese species, and what 

 could be done for the one could doubtless be accomplished for the 

 other. 



Mr. Ryder turned his special attention to the American form. Dur- 

 ing the past season he found, after opening the animal carefully, that it 

 is easy to remove the ova and milt from the female and male by strok- 

 ing the generative ducts towards their outlet, when the products can 

 be picked up with a pipette or " medicine dropper " and transferred to 

 water free from extraneous matters of every kind. He also found that 

 when the milky mass is dropped into water the character of the cloud 

 of particles produced in the water at once diagnoses the sex of the 

 individual from which the spawn has been obtained. If the animal be 

 a male the cloud produced upon stirring breaks up into wisps and 

 streaks, which resemble the cirrus clouds or mare's tails of meteorolo- 

 gists. If the specimen be a female the spawn when dropped into the 

 water immediately breaks up into a distinctly granular cloud. These 

 differences are so marked that any person may be taught to recognize 

 them in a few minutes. The new method of removing the spawn and 

 milt from the reproductive organs insures greater success in impregna- 

 tion. Mnety per cent, of the eggs may be fertilized by the new methotl, 

 a result scarcely possible with the usual plan of chopping up the re- 

 productive organs. This method, together with the mode of discrimi- 

 nating the sexes without the use of a microscope, puts us in a fair way 

 to realize some part of a scheme of artificial proi^agation. 



Mr. Ryder also ascertained the nature of the collapse and shrinking 

 of the oyster body about the end of the breeding season. It is due to 

 a total atrophy or wasting away of the reproductive organs at the com 

 pletion of the spawning season. The whole of the connective tissue sub 

 H. Mis. 26— —58 



