The lactic dehydrogenase activities of Ascaris lumbricoides have been assayed according to the developmental course of the fertilized eggs compared with the unfertilized eggs. Experimental procedures were modified that of Wroblewski and La Due's method with use of diphosphopyridine nucleotide reduced form(DPNH). Sodium pyruvate and lactic dehydrogenase, the specific activities were expressed as DPNH unit per mg protein by method of Kornberg's. The experimental results are as follaws: Lactic dehydrogenase activity in fertilized eggs of Ascaris are significantly increased from morula stage and its optimal pH is in 3.4 degrees. While any activities were not observed in unicell stage of fertilized eggs and unfertilized eggs. Water soluble protein of fertilized eggs of Ascaris were varied in their amount during their developmental process. The amont of protein in tadpole stage eggs have increased to 1.3 times more than that of cleavage stage eggs. However the amounts of water soluble protein in unfertilized eggs are revealed to one-third less than that of fertlized eggs. The specific activity of lactic dehydrogenase in tadpole stage eggs are decreased to one third less than those of morula stage eggs during development, the stage is considered to be as a growth criteria in developmental process, as on this point the activity of aerobic cytochrome c oxidase and cyclophorase begin to increase respectively.
