9o8 



GENERAL METABOLISM 



[PT, ITI 



Fig. 240. 



the second hour; this is due to the formation of the perivitelHne 

 fluid (see p. 784). According 

 to Bialascewicz, this tempor- 

 ary reduction and the forma- 

 tion of the perivitelHne space 

 only occurred in fertilised eggs, 

 as Fig. 240 shows, but perhaps , 

 the difference is quantitative -i 

 rather than quaHtative. In .■ 

 the later stages Bialascewicz - 

 measured the volume directly I 

 instead of calculating it from ; 

 the measured diameter, and . 

 his results appear in Fig. 241, 

 taken from his paper, where 

 the average volume of one 

 larva is plotted against the 

 time in days. The shape of this 

 curve is of interest, inasmuch 

 as there is first of all a marked rise, followed by a compara- 

 tively stationary period during the last few days of the pre-hatching 

 period, and then by a tremendous 

 rise as soon as the larva has come 

 forth from its jelly, and nothing 

 interposes itself between the tissues 

 and the water but the skin. These 

 data are obviously in close agree- 

 ment with the findings of Kronfeld 

 & Scheminzki and of Gray. Thus 

 Bialascewicz found that between 

 the 2-cell stage and the blastula 

 stage there was an increase in 

 volume of (average) io-6 per cent., 

 and between the blastula stage and 

 the gastrula stage an increase of 

 7*6 per cent. Fig. 242 shows the 

 relative speed of volume increase 

 at the different stages expressed in terms of volume increase of 

 1000 larvae in hourly periods. The higher level at gastrulation 



1 2 3 4 5 6 7 8 9 10 1112 13 

 Fig. 241. 



