8o ORIGIN OF POLARITY, SYMMETRY, AND ASYMMETRY 



between these results and those on the newt is doubtless to be ex- 

 plained as a result of the precocious appearance of bilaterality in the 

 egg of Amphioxus, extending to chemo-diiTerentiated substances, 

 which is established immediately after fertilisation. As suggested 



Fig. 34 

 Double monster of Amphioxus, produced by mechanical disarrangement and 

 partial separation of the blastomeres in the 2-cell stage. Note that both com- 

 ponents show normal asymmetry, i^, ist gill-cleft; eg, club-shaped gland; 

 m, mouth; p, preoral pit. (From Conklin, Journ. Exp. Zool. lxiv, 1933.) 



in the preceding paragraph, this rigid bilaterality might establish 

 an equally rigid asymmetry-gradient (fig. 34). 



§4 

 The conclusions arrived at from a consideration of the results 

 obtained from experiments on amphibian development are sup- 

 ported and extended by experiments on Echinoderm larvae. In 



