65 



size alone oxcepted, the i^rocess was nerfectly normal." 



To my krcwledge Haeckol was the first lc rublish the 

 statement that halves of hydro-,edusa egps would develop) into 

 norr.al eiribryos. For sor.e time naturalists in general v/ere 

 inclined lo doubt the fact^ but since the work of Boveri, 

 Hertwir brothers, Roux, Driesch, Viilscn, Korgan, Loeb and 

 others on the fragments of eggs, the development of ei^ibryos , 

 abnormal and normal, from the portions of eggs is a question 

 no longer to be doubted. 



FORMATIOi: OF THE ECTODERM. 



In ihe develCvH-.e-it of the egg of Turr iter sis the ger- 

 minal layers are not differentiated by process of eribole, 

 delamination or cellular ingression. During segmentation 

 the blastoreres do nrt separate and arrange themselves around 

 a segmentation cavity which later is transformed into a 

 b^a-stocoele. Thus instead of having fcr-ed a coeloblastula, 

 we find that cleavage results in the formation of a solid 



