THE ORGANIZATION OF THE EGG AND THE DEVEL- 

 OPMENT OF SINGLE BLASTOMERES OF 

 PHALLUSIA MAMILLATA 



EDWIN G. CONKLIN 



Princeton University 



FOURTEEN FIGURES 



In view of the fact that Driesch ('05) has stated that the eggs 

 of Phallusia mamillata show none of the ooplasmic differentia- 

 tions which I ('05) had observed in the eggs of other ascidians 

 and since he has maintained ('96, '05) that the ^ or | blastomere 

 of Phallusia may give rise to an entire gastrula and larva, con- 

 trary to the observations of Chabry ('87) and of myself ('05) on 

 other ascidians, it has seemed to me desirable to reinvestigate 

 the egg of Phallusia in order to determine, if possible, whether 

 it differs from other ascidian eggs in these respects. A residence 

 of several months at the Stazione Zoologica at Naples, ^ during 

 the spring of 1910 enabled me to study the organization and cell 

 lineage of the eggs of Phallusia and to repeat Driesch 's experi- 

 ments. 



THE NORMAL EGG AND EMBRYO OF PHALLUSIA 



The living egg of Phallusia mamillata is, as Driesch ('05, p. 

 661) has said ''glashell und lasst nichts von den verschiedenen 

 Stoffen Conklin erkennen." There are no pigments in the egg 

 itself nor any visible granules of yolk or other materials. A 

 green pigment is found in the 'test cells' (follicular cells) but 

 this does not color the protoplasm of the egg. Furthermore I 



II wish here to acknowledge my great indebtedness to the Director, Dr. Rein- 

 hart Dohrn, and to the other officers of the Station for their generous assistance 

 and constant courtesy. 



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