346 GRACE MEDES 



age of 96 hours, but for the last 24 hours growth had practically 

 ceased. During the entire period, however, this culture was 

 well within the range of the control culture, F, plot 1. In /+, 

 the eggs underwent cleavage, but did not develop further. 



The modifications in the skeleton in these diluted solutions 

 were of the same type as in the preceding experiment, — a re- 

 duction in the size and number of processes and a delayed fusion 

 of the lateral connectives and of the body-rods (fig. 26). This 

 tendency toward reduction in skeletal structures seemed to 

 have no correlation with increase or decrease of size, since it 

 was displayed by those larger as well as by those smaller than 

 the control. 



Conversely, in the solutions of greater concentrations a tend- 

 ency toward increased complexity of structure appears, accom- 

 panied by the reduction in size described above. Figures 27 

 to 31 illustrate one individual from the control and one from 

 each of the more concentrated solutions after 96 hours. Figure 

 26 is taken from d, 15 per cent dilution, on the same day. This 

 increased complexity of structure is shown by the greater promi- 

 nence of the spines as well as by the greater size and number 

 of the processes on the posterior part of the body-rods. In 

 contrast to the delayed fusion of the individual elements in the 

 diluted solutions, those in the concentrated ones show a tend- 

 ency, not only toward early fusion, but also toward excessive 

 depositing of calcareous material at the points of contact of the 

 transverse rods. 



As the limits of endurance are approached in the more di- 

 luted and concentrated solutions, a tendency toward irregu- 

 larity of structure appears. This is illustrated somewhat in 

 figure 26, where an accessory spine on the right side of the 

 larva near the base of the arm-rods, interrupts the otherwise 

 highly symmetrical condition. It is shown more clearly in the 

 following drawings (figs. 27 to 31), where each increased concen- 

 tration produces a higher degree of irregularity. 



The third experiment in this first series was undertaken for 

 the purpose of observing whether the organism would undergo 



