PLATE XLV. 



Cleavage of Isolated Blastomeres. 



cells 



Fig. 30. Exp. 906: Third cleavage in § or f blastomeres, separated by pressure; the 

 smaller than the normal macromeres, owing probably to loss of yolk during pressure ; each cell is dividing 

 dexiotropically as it should in the third cleavage, but the relative positions of spindles and cytoplasmic 

 areas in the two cells have undergone certain changes as may be seen by comparison with fig. 20. 



Fig. 31. Exp. 921: i or f blastomeres, separated by shaking; the spindles are normal in position 



though division in B has been delayed. 



Fig. 32. Exp. 855: i blastomere, isolated by shaking; the first micromere has been formed and 

 the second is forming in typical manner. Original animal pole indicated by polar bodies. 



Fig. 33. Exp. 855 : t blastomere, isolated by shaking ; the first and second micromeres have formed 

 in normal manner, and the former is dividing as in a whole egg. Original animal pole indicated by polar 



body* 



Fig. 34. No. 714: £ blastomeres, probably separated by pressure; each macromere has given off a 



micromere in dexiotropic direction, as in whole eggs. 



Fig. 35. Exp. 855: \ or } blastomeres, separated by shaking; each has produced a first micromere 

 in dexiotropic and a second in Inotropic direction, and the former are dividing in laeotropic direction just 

 as in whole eggs. The micromere plate is a continuous one, without breaks. 



Fig. 36. No. 711: f blastomeres, one macromere having been separated, probably by pressure. 



macromere has formed one micromere in normal fashion, but a gap 



and 



Fig. 37. Exp. 864 : J or f blastomeres, separated by hypertonic sea wat 

 water 10 hrs. Each macromere has formed three micromeres, and the first 



subdivided in normal fashion. The egg is a whole in the sense only that it shows no gaps where cells are 



missing. , . 



Fig. 38. No. 715: \ egg, probably separated by pressure after third cleavage, as shown by the fact 



that two micromeres of the first set (la and 16) are present. 



Fig. 39. Exp. 875: f blastomeres, macromere C having been destroyed in dilute sea water; tne 

 macromeres have given off the first micromeres, and these have subdivided in typical fashion, forming a 



triangular, but continuous micromere plate. . . fl 



Fig. 40. Exp. 958: f blastomeres, separated by shaking. Cells A and D have given rise to nrst 

 and second micromeres in normal manner; B has formed only the first micromere and both 15 and lo lac* 

 nuclei. 



™ 41. Exp. 867: f blastomeres, separated in hypertonic sea water. Typical cleavage of micro- 

 meres and macromeres of each quadrant represented, but the cells of one quadrant are wholly lacking. 



Fig 



each 



three 



Fig. 42. Exp. 1002 (2) : £ blastomeres, separated by pressure. Cleavage typical ic 

 but delayed in quadrant B ; the third micromere is j ust coming off from 2D. 



Fig. 43. Exp. 958: f blastomeres, separated by shaking. The cleavage of these 

 A, C, and D is absolutely typical; the cells of the fourth quadrant (C) are entirely lacking, but ^re a 

 gaps to mark the places from which they have dropped out. Each macromere has Placed ^"^^ 

 meres, and in addition D has given rise to a fourth, the mesentoblast, 4d(= M , M ). ine 

 have each divided in typical manner, giving rise to a cross (stippled cells) with three arms insteaa 



Fig. 44. Exp. 959: f blastomeres separated by shaking; the cleavage of each macromere ana 

 subdivisions of each micromere have taken place as in normal eggs. 



