(10) 



It is agreed that tl:e segmentatiori is total, Toettincer (o) 



ard '^'. Schultz (21) claim that the aegneii tat ion is unequal. 



(5) 

 Caldwell^ says that in ti:e four-cell stage two srualler clear aa^d 



two larger opaque cells are f resent, Masternian (16) finds tiiat 

 in the for^r-ecll stage the bl astonieres taper toward one pole 

 and that this results, v/hen tl.e third f.irrow appears, in the 

 upper four being less in bulk than the lower four, Masterraan's 

 description, ^ find, applies to the eggs of Phoronis Australia. 

 Ikeda (9) did not discover any appreciable difference in the 

 size of the blastomeres until tne eignt-ccll sta^o. At tuis 

 time , he says, "it will be seen that tne upper four blasto- 

 meres are very slightly smsJlcr tiian tne Ic.^r fj^'-, « 



In Phoronis architecta the •f'irst cleavag? plane is merid- 

 ional and usually divides the egg into tv/o practically equal 

 blastomeres ("Pig. 3) altr.ouj-h sci/ietimes the division is decid- 

 edly unequal, (Fig. 4) The cleavage fi;rrow begins in the re- 

 gion of the polar bodies. ("Pig. 5) After the completion of 

 tiie first cleavage and sometimes before, the first polar body 

 divides. (Fi^.o) In "^ig.b ia seen the reconstruction of the 

 nuclei after the first cleavage. Immediately before the sec- 

 oua cleavage the two blastomeres uhich were closely applied 

 to one another after the first cleavage come to overlap. 

 About fifteen minutes aftc*- the firat cioavage, thn second 



