214 CHAS. W. HARGITT. 



ORGANIZATION OF THE EGG. 



It has long been known that simple though the egg may be 

 it must, nevertheless, be regarded as potentially highly complex. 

 Concerning the early views of His, Whitman, Flemming and 

 other earlier investigators, no attempt will be made here to give 

 special citations. The later experiments of Roux, on the devel- 

 opment of the frog's egg, supplemented by similar experiments 

 by Driesch '95, served to emphasize still further the general view 

 here stated. 



The still later investigations of Wilson ('03, '04), and Conklin 

 ('05', 'o5 2 , 'O5 3 ), have given a new impulse to researches along 

 this line, and have clarified and measurably harmonized the con- 

 flicting views of earlier observers. 



So far as I am aware, no one has shown any evidence of any- 

 thing of a similar character in the organization of the eggs of 

 codenterates. In commenting on the account given by the pres- 

 ent writer of the cleavage of the egg of Pcnnaria Conklin ('o5 3 ), 

 has suggested the probability that predetermining factors must 

 be present in some form. " Even in such eggs as that of Pen- 

 naria it is certain there must be determining factors somewhere, 

 if not in the cytoplasm then in the nucleus, which determines that 

 the egg shall develop into a pennaria rather than into some other 

 animal ; it is further evident that these determining factors must 

 be present in the cytoplasm at a relatively early stage, if not in 

 the very beginning of development " (p. 215). 



Hence in my studies on hydroid eggs rather particular atten- 

 tion was given to this point with the hope that some evidence 

 might be found for or against the views in question. In my work 

 on Pcnnaria ('O4 3 ), while no direct evidence of cytoplasmic dif- 

 ferentiation was found in the living egg, there was found in some 

 cases after fixation by certain reagents, more particularly the 

 picro-sulfuric solutions, what seemed to be a stratified, or con- 

 centric arrangement of the cytoplasm. At first I was inclined to 

 regard this as probably significant of such locally differentiated 

 matter as might go to form the ectoderm. But since this condi- 

 tion was not found to be constant it was regarded as probably 

 an artifact, due to the action of the reagent. A recent examina- 

 tion of my earlier preparations has not suggested any change of 



