13 

 Ir.rpor thar the ursepFPrtcci err. The avfra^e r.i2c c.r several 

 blactulpe that were reacurec' war .19 nr. ii" lenpth a-^d .15 

 mr. ir their larre?t transverse diareter. The epr before 

 cleavage '-easured , as stated before, ,14 tt. ir di^areter. 

 The blastoreres i'^ the blastula r^tape have berr-e very 

 -unerous a^d ?~all, ard are arrarf^ed ir a zi^.f.'e layer of 

 epithelial cells, V.hen the larva ir. about eif^ht or ten 

 hcur2 eld, these "oerirheral cell? '■''evelOT- cilia; nrcbably 

 each cell has one ciliuir. Vith the develorrert of the cilia 

 roverert cctr-e'-ces . At first the nrtic is sllrbt; b',:t 

 as the cilia beccre -"-ore ru-erous, the blartula is er?-bled 



by the ciliary rrvererts tc leave the bctto- rf the aauariur 



-to- 

 urer rhich it vas heretofore lyirp a-d^svir a'-cut 1- the 



v.-ater with s sriral cr ccrk-r^crew motior v^Mch is charac- 

 teristic of hydrod blastulae ard rlrrulre. Ihe larpe erd 

 of thp blastula is r'irtcted forwrrd a-d therefore rray be 

 called the a'terior e-d. 'hether .hr rnterior rart of the 

 larva ccrresrcnds c the ur er or Icv/er role of the egg was 



