CLEAVAGE IN THE EGG OF CEREBKATULUS. 5 



III. Experiment C (C lacteus). 



A portion of cytoplasm is removed by a single cut from both 

 the blastomeres during the first cleavage. Six eggs were thus 

 operated on. All divided irregularly excepting two, which devia- 

 ted a little from the normal mode as shown in Fig. 8a-c. This 

 may be due to the fact that the sections were horizontal or nearly 

 so in either case. 



rV. Experiment D (C. lacteus). 



Close to the end of the first cleava2;e, when the two blasto- 

 meres were still connected by a narrow bridge, the cells were 

 separated from each other by a vertical cut and the cleavage of 

 each blastomere was studied. Sixteen cases were examined and 

 it was found that every one of them performed a partial cleavage 

 exactly like the isolated blastomeres of the 2-cell stage. Some 

 gave rise to closed blastulas, others to open ones. This result 

 confirms Zeleny's observation made on the egg of C. onarginatus 

 ('04, pp. 308, 309, 322). 



V. Experiment E (C. lacteus). 



At the 2-cell stage a portion of cytoplasm was cut off from 

 the vegital region by a horizontal or oblique section, and at the 

 8-cell stage the size of the upper (the fiist quartet) and the lower 

 blastomeres were compared.^ Nine eggs were thus operated on, 

 and it was found that in every case, irrespective of the angle of 



1 This experiment was carried uut at tlie Haipswell Laboratory in the summer of 1907, 

 suggested by a similar experiment which had been performed upon the egg of Bero'é nearly 

 a year before at Naples. 



