332 



GRACE MEDES 



A week of almost complete rest followed, succeeded by a period 

 of sexual maturity, which also showed an early maximum 

 and a gradual decline in the proportion of ripe individuals. 

 By the middle of September all the females possessed pale and 

 exhausted ovaries, while the males were to a large extent active. 

 The spermatozoa, however, were less vigorous than those ob- 

 tained early and became inactive in a much shorter time after 

 extrusion. 



Plot 1 gives the general growth curves *of the control cultures 

 taken during the entire period of experimentation. Hours 

 after fertilization are plotted as absissa, size as ordinate. A 

 represents the average of four control cultures run during 

 August and the two weeks of September 1914; B, 24 during the 

 early part of the following summer; and C, nine during the 

 latter half of July, 1915. A and C were taken during corre- 

 sponding periods of egg-production and were arranged thus for 

 the purpose of comparing the general growth curves of the 

 two years. D represents the measurements of all the control 

 cultures for the entire period. E and F are lines drawn through 

 the extreme variants in the control averages. 



Averages of the control cultures of the various periods 



Before taking up a more detailed consideration of the sepa- 

 rate cultures, some general observations may be drawn from 

 these figures. D, the average of 3600 individuals raised during 

 widely varying seasons of two successive summers, may be 

 taken as our standard growth-curve. When the embryo was 

 24 hours old, the skeleton measured 15.31 and extended nearly 

 through the body. Figure 1 represents a normal skeleton of 

 approximately this size. When the normal individual was 48 

 hours old, the four arms were well developed and the skeleton 



