ASYMMETRY IX THE STARFISH. 127 



/ 



Second Census (One week old). 

 Control. . . .92% of larvae with left water pore and pore canal 



8% ' right 



2, A (iced i hr.) 86% left 



13% right 



i% " " " bilateral " 



2, B (iced 2.5 hrs.) 76%" " " left 



24% right 



EXPERIMENT 3. 



Twenty hours after fertilization, when all larvae were free- 

 swimming blastulae or early gastrulae, they were divided into three 

 lots: one the control, one iced one and a quarter hours, and the 

 third iced tw r o and a quarter hours. 



First Census (5 days old). 



Control 84% of larvae with left posterior coelom 



16% " " " right 



3, A (iced 1.25 hrs.) 69% left 



24% ' right 



7% " " " median 



3, B (iced 2.25 hrs.) 77%" " " left 



19% " " " right 



4% " " " median 



Note: There was one specimen in Lot 3, B (iced 2.25 hrs.), which had two full- 

 sized posterior cceloms on the left side, one behind the other. This might be 

 interpreted as incipient metamerism. 



Second Census (one week old). 

 Control 87 % of larvae with left asymmetry 



13% ' right 



3, A (iced 1.25 hrs.) 8i%" " " left 



16% ' right 



3 % ' bilateral symmetry 



3, B (iced 2.25 hrs.) 83% left asymmetry 



14% right 



3% ' bilateral symmetry 



Note: This experiment shows only a slight increase in the percentage of reversed 

 asymmetry through icing. It should be noted, however, that a large percentage of 

 the larvae, though not quite so old as those in Experiment 2, were beginning gastru- 

 lation and thus past the period of maximum susceptibility to symmetry reversal. 

 This will be shown more clearly in Experiments 8 and 9. 



EXPERIMENTS 4, 5, 6, 7, 8, 9. 



Six different lots of eggs from six different females, fertilized by 

 the sperm of one male, were dealt with exactly alike except that 

 some w T ere allowed to develop a few hours longer before icing, and 



