Processes of the Ecliinoderm Egg during Fertilisation. 417 



so rendering comparison of the oxygen intake with the heat production 

 impossible. It is essential in experiments of this kind that in both the 

 oxygen and C0 2 , and also the heat determinations, all the eggs should fertilise 

 at the same time, and that, after fertilisation, they should all develop at the 

 same rate, as otherwise no comparisons can be made between different 

 portions of the experiment. In all, out of some 500 experiments few were 

 satisfactory in all respects. 



To simplify matters the manometer readings in the following experiments 

 have all been reduced to standard barometric (760 mm. Hg.) pressure and 

 uniform temperature of 14"5° C. The galvanometer scale readings have 

 also been adjusted to start from zero, although it was seldom possible to 

 adjust the temperature of the two flasks so closely that the readings should 

 actually commence at zero. The galvanometer mirror deflection being always 

 either to the right or left the zero was in the middle of the screen. The 

 thermocouple was arranged so that the hottest junction should always deflect 

 the mirror to the right. 



Experiment 1. 



(a) Heat Determination. — 400 c.c. of ripe well washed E. miliaria eggs in 

 sea- water were placed in Flask K, and 380 c.c. sea-water in Flask No. 7, under 

 the conditions of the experiment both flasks had the same coefficient of heat 

 loss. The flasks were sunk down in the bath water, with the thermocouple 

 junctions and air tubes in place. The temperature of the flasks was adjusted 

 to within a hundredth of a degree of the temperature of the bath, and the 

 flasks allowed to remain with air bubbling through them for half-an-hour. 

 The flasks were closed with thick wads of cotton-wool. At the end of this 

 time the temperature of the flasks was again adjusted as near as possible to 

 that of the bath, and after a few minutes a few drops of sperm were added to 

 the eggs, and the cotton plugs with air tubes and thermocouple junctions 

 replaced in the flasks and galvanometer readings commenced. 



Time 3 p.m. galvanometer scale reading was 



4 „ „ „ 5 mm. to E containing eggs. 



5 „ 



6 „ 

 11 „ 



2 A.M.* 



7 



10 

 21 



28 



At the end of the experiment 98-100 per cent, of the eggs in the flask 



* In carrying out an experiment the preliminary preparations often took up so much 

 time that the actual galvanometer readings could only be started late in the day and had 

 sometimes to be carried through to the following morning. 



2 G 2 



