PROGRESS JN BIOLOGICAL INOUIKIKS bo 



were raised in the laboratory tanks from artiticially fertilized eggs, 

 only 3 or 4 day old larvie being used for the experiments. The re- 

 sults show that the increase of hydrogen-ion concentration has a 

 marked eft'e('t on the vitality of the larva\ At a pH of 5.8, G4 per 

 cent die within 11 hours; at a i)H of 5.4, 100 per cent die in 7 hours; 

 wdiile water having a pH of 5.2 kills them almost instantly. 



It is a matter of couimon knowledge that the union of si)erm and 

 egg of many marine organisms is greatly atfeqted by the environ- 

 ment, but information relative to the fertilization of oyster eggs is 

 lacking. First a series of tests Avas made to determine the necessary 

 dilution of sperm in artificial fertili/.ation- The best results were 

 obtained when the dilution of 1 : 40,000 was used; in a denser suspen- 

 sion polyspermy takes place and the development of the egg is hamp- 

 ered. 



The viabilit}^ of sperm and eggs in sea water was also studied. It 

 was found that 12 hours after spawning the sperm becomes inactive 

 and does not penetrate the egg. The viability of the eggs is longer, 

 but eggs fertilized after being left for six hours in sea water give a 

 great percentage of irregular development. Both sperm and eggs are 

 very susceptible to changes in the reaction of Avater. The increase 

 of hydrogen-i(m concentration affects them, and when the pH value 

 is lowered from S.l, which is normal for Woods Plole water, to 7.0 

 only a small percentage of the eggs is fertilized and develops, while 

 in the control 99 per cent develop into larva?. 



In the sunnner of 1923 experiments were undertaken by Herbert 

 F. Prytherch to determine a metiiod Avhereby oysters might be arti- 

 ficially propagated and, if possible, to deA'elop the method to such an 

 <'xtent as to make it of practical commercial value. A small hatchery 

 Avas built at the ])lant of the Connecticut Oyster Farms Co., at Mil- 

 ford, Conn., and \arious types of apparatus Avere tested out for rear- 

 ing the larval oysters. By carefully imitating natural conditions a 

 neAv method Avas perfected by Avhich over 1,000 oyster larvai Avero 

 reared from the egg until they attached to the collectors. These ex- 

 l^eriments Avere continued during the summer of 1924, the chief object 

 being to impi'ove the method to such an extent that sufficiently large 

 numbers of oysters might be produced to make the process of prac- 

 tical value to the oyster industry. 



The equipment, Avhich Avas successfully used the previous summer, 

 Avas again i)ut in opei'ation after making a fcAv minor changes in 

 the arrangement of the filters. During the latter part of July, in a 

 battery of small Avooden tanks, several lots of oyster larvae were 

 I'eared, and from these oA'er 5,000 spat Avere collected. The output 

 of such a small hatchery could hardly be sufficient to demonstrate 

 the A^alue of the method for connnercial purposes, so in order to get 

 as great a production of oysters as possible additional equij^ment Avas 

 installed. This consisted of a tile hatchery trough 100 feet long and 

 havin<; a cai)acity of 300 gallons, in Avhich the Avater Avas continually 

 replenished and circulated by means of electrical devices. SeA-eral 

 million oyster larva? and a feAv thousand hard-clam larA^se Avere 

 reared successfully in the large trough for a period of 10 days, Avhen 

 an unforseen accident, folloAving a violent Avind and rainstorm, sud- 

 <lenly terminated the experiment. 



