LARVAE OF ARBACIA PUNCTULATA 381 



behind the control. In solutions more highly alkahne, the 

 excessively precocious developmen.t results in irregularity and 

 asymmetry and finally in complete inhibition. 



Loeb ('98) in an early paper called attention to this effect 

 of acids and alkalies upon the rate of development. He stated, 

 however, that alkalinity produced a scarcely noticeable effect 

 in the first few hours, and a gradually increasing one on the 

 second and third days. "So gewinnt man den Eindruck," he 

 says, "als ob die Hydroxyhonen des AlkaU eine langsame aber 

 stetige Zunahme in der Geschwindigkeit der Entwicklung 

 bedingen." But after three or more days, disintegration of the 

 larvae set in and he could no longer determine any difference 

 between those in alkaline solutions and those in sea-water. 

 He suggested that by this time the alkali was largely neutraUzed 

 by the acids produced in the process of growth. 



Later, in his ''Artificial Parthenogenesis and Fertihzation" 

 he takes an entirely different position. He says that "he has 

 since vainly attempted to show that the rate of development 

 of the sea-urchin egg can be increased with the increase of the 

 concentration of hydroxylions in the sea-water. This leads 

 him to believe that these eggs develop best in a solution in 

 which the concentration of hydroxylions equals that of the sea- 

 water; and that while it is possible to delay their development 

 by a lowering of this concentration, no acceleration can be 

 produced if the Cqh in the sea-water is raised." 



That some effect upon rate of development is produced in the 

 earliest stages, was demonstrated by the following experiment 

 in which solutions of the same constitution as in Experiment 11 

 were employed. Each culture was divided into two portions 

 and at one hour after insemination one of each was killed quickly 

 by the introduction of a few drops of fixing fluid, and a count 

 taken of the number in the one- and two-cell stages. After 18 

 hours, the percentage of those possessing skeletons was taken in 

 the other portions. 



