138 RALPH S. LILL1E. 



their behavior than later in the season. The general character 

 of the results following simple exposure to butyric acid solutions 

 for varying periods has already been described in my two pre- 

 ceding papers; detailed descriptions of separate series are there- 

 fore unnecessary, and the essential results can be presented most 

 concisely in the form of tables. Table I summarizes the results 

 of ten typical series of experiments at temperatures of 8 to 28- 

 The experiments are divided into two groups, A and B, one 

 carried out early in June, the other two weeks later. My ex- 

 perience of the last three summers has shown that the effective 

 durations of exposure, both to warm sea-water and to butyric 

 acid solution, are decidedly longer early in the breeding season 

 (up to the middle of June) than later. This is illustrated by the 

 two series of experiments at 18 in Table I.; thus on June 10 

 the optimum exposure was about 14 minutes; two weeks later 

 (June 24) it had fallen to about 6 minutes. 1 The physiological 

 condition of the eggs used in each group may be regarded as 

 approximately uniform, although certain individual differences of 

 susceptibility are apparent. In both groups the condition of the 

 eggs was good throughout, practically all eggs in the control 

 dishes undergoing normal maturation and developing to larval 

 stages after fertilization ; but in the later group the physiologically 

 equivalent exposures are on the average only about half as long 

 as in the earlier. Experiments performed during the intervening 

 period (June 13 to 21) show intermediate conditions (see Table 

 IV). 



The estimates of temperature-coefficients for a given temper- 

 ature-interval (e. g., 8 to 10) were always made from results 

 obtained with a single lot of eggs; these eggs in nearly all cases 

 came from a single animal. The eggs used in determining each 

 temperature-coefficient thus form a homogeneous group. The 

 total number of series of experiments, each with a separate lot 

 of eggs, performed during the whole period of May 30 to June 

 28 was twenty-three. Table IV at the end of the paper gives a 

 summary of the character and essential results of all of these 

 experiments. 



1 Compare the optima for the same concentrations of butyric acid given in 

 Table III (June 7-13, 1915) and Table V (July and August, 1915) in my article 

 in Journ. Biol. Chem., loc. cit., pp. 243 and 246. 



