126 H. H. NEWMAN. 



Summary of Experiment i. 



1. There was a fairly high percentage of control larvae in the 

 first census showing reversed asymmetry of the posterior coelom, 

 but the numbers of control larvae with reversed asymmetry in the 

 later censuses was very small, only 3 per cent, and 2 per cent, 

 respectively. 



2. In every census (9 in all) the experimental cultures showed a 

 much higher percentage of reversed larvae than the controls. The 

 average per cent, of reversed larvae in experimental lots was 30.44, 

 as compared with 4.66 for the controls. Thus there was over six 

 times as high a percentage of symmetry reversal in experimental 

 lots as in controls. 



3. In Lot i, C (iced 3 hours) there were many bilateral larvae, 

 only one of these appearing in any of the other lots. 



4. The conclusion seems obvious that in this experiment the 

 percentage of instances of symmetry reversal has been very 

 markedly increased by retarding the development of the blastulae. 

 In other words, reversal of asymmetry and bilateral symmetry 

 have both been induced experimentally. 



5. To determine whether this experiment is exceptional or 

 typical, eight other experiments were carried out using the same 

 materials and methods, but with some variations in the stages at 

 which the larvae were iced and in the length of exposure to low 

 temperatures. 



EXPERIMENT 2. 



Twenty-one hours after fertilization, when all larvae were 

 hatched and swimming about as late blastulae and early gastrulae, 

 they were divided into three lots. One was left as a control, a 

 second iced for one hour, and a third iced for two and one half 

 hours. 



First Census (5 days old). 



Control 94 % of larvae with left posterior coelom 



6% " " " right 



2, A (iced i hr.) 81% left 



6% " " " right 



13% " " " median 



2, B (iced 2.5 hrs.) 63%" " " left 



31%) right 



6% " " " median 



