Nos. 451-452.] AMERICAN SOCIEl J OF ZOOLOUlS /A 



499 



next stage there is no distinct equatorial groove, 

 stage is gradually derived from the four-cell 

 condition by the appearance of furrows be- / 

 tween the two original ones. In the eggs ot / 

 this stage which Wilder has studied (see foot- \ 

 note) two rather regular vertical planes of 

 cleavage cut the egg at nearly right angles to ^.^ 

 the first division plane, but in a considerable 

 number of eggs which I have examined, some 

 of them living and others preserved, I onU ton 

 with such regular vertical cleavage planes; in soiu 

 approach to it, but in a number of others tlu- 



seemed to be gradually (k-ii\r(l 

 cell stage by the appearance of 

 were hard to recognize as pa 

 planes ot cleavage. In the e 

 the first furrow nearly encircle 

 the position of the first and 



Fig. 5.- Surface views of a oftCU SO shiftcd thai it isdltf 



lidelawTil^'"" ^^^^ they were ever at ii^ht . 



At this time the animal i)(»le 1 

 into one or more distinct blastomeres, but the \ 

 shows almost no signs of cleavage planes (1m<;. 4) 

 As segmentation proceeds the surface appe.--^" 

 in general with those of other amphibian ova 

 (Fig. 5), but sections bring out the fact that 

 the segmentation is shallow, and does 

 volve the whole thickness of the egg (Fig 

 Later, however, when the i 

 is like that ot a fine celled 



I he eight eel 



