LOW TEMPERATURE — DEVELOPMENT OF FUNDULUS 473 



of the egg and embryo themselves; and I beheve that these are 

 not merely different phases of the action of a single principle, 

 certainly not all due to a lack of 'developmental vigor' although 

 that is a pretty general phrase and one that might cover a mul- 

 titude of varied conditions, individually unlike and due to varied 

 primary causes. 



Turning now to a much briefer consideration of Werber's 

 hypothesis, as stated above, I shall refer only to his latest papers 

 ('15, '16). While admitting that the nutrition hypothesis may 

 account for the production of certain types of human monsters, 

 Werber rejects its general validity in favor of the view that 

 modifications in the physical or chemical environment, for 

 example in the blood of the parent organism, affect directly 

 either the germ cells before fertihzation or the fertilized ovum or 

 later developmental stages ('15 a, p. 530). Thus he agrees with 

 Spemann in opposing the hypothesis of Stockard mentioned 

 above, regarding the cause of cyclopia, and beheves that the 

 eye-defects, which form the main subject of disagreement here, 

 are really due to morphological defects of some kind, and not 

 to an inhibition resulting from lack of developmental vigor or 

 energ3'. He goes farther than this, however, and suggests that 

 the substances used in his experiments, namely, butyric acid and 

 acetone, caused ''an elimination of materials of the blastomeres 

 or of the germ-disc and probably also of the yolk-sac." "Blas- 

 tolysis either destroys part or all of the germ's substance, or it 

 may split off and disperse parts of the latter" ('16). And fur- 

 ther "This ehmination of material may be due either to the 

 precipitating or solvent effect respectively of the chemicals 

 which were used" ('15 a, p. 559). From the examination of 

 ver}' extensive material he concludes that "either the blasto- 

 meres or the germ-disc had been blastolytically fragmented 

 owing probably to both physical and chemical factors" (p. 559), 

 and that whatever scattered parts survive this fragmenting and 

 blastolytic process "may go on developing into a whole defec- 

 tive [sic] or a meroplastic, embryo, or even into an isolated 

 organ" (p. 559). And in another place ('15 b) he adds that an 

 increased imbibition of water following an increase in the per- 



THE AMERICAN JOURNAL OF ANATOMY, VOL. 20, NO. 3 



