€ Art. 3.— Naohide Yatsn : 



•examine two cleavage stages of the egg of Berœ forskhlii (PI. II, 

 Figs. 10 and 20). In this particular egg the second cleavage has 

 begun before the first has come down nearly two thirds of this 

 •entire course. By the precocious second division tlie typical 

 alveolar arrangement has been considerably disturbed, a flow-figure 

 having been formed in each blastomere. For all that, the first 

 •cleavage cuts through the egg normally as through nothing had 

 happened near the macromere pole. 



Pari paH.m with the coming-down of the cleavage furrow, the 

 •ectoplasm thickens near the micromere pole as has been observed 

 by ZiEGLER. And the "cleavage head" meets the ectoplasmic 

 <iccumulation there (PI. II, Fig. 15,). The walls (,f the cleavage 

 furroAv near the "head" become irregularly wrinkled and the spin- 

 ning activity increases (cf. Andrews '98). The hole now assumes 

 a triangular shape. As the entoplasmic alveoles quickly retreat, 

 the ectoplasmic bi'idgc' is left; between two fartmeres (PI. II, 

 Figs. 17, 18, 21, 21). It is interesting to recall that LoEB observed 

 •cytoplasm flow away from the furrow towards the end of unilateral 

 •cleavage ('06 p. OG). No particular movement as seen by Bunting 

 in Hijdraciinia ('04 p. 216) takes place {cf. Ziegler's experiments). 

 Finally the ectoplasm also goes into the blastomeres, leaving 

 behind a fine thread of homogeneous layer. By the time one 

 finds an ectoplasmic thickening with radially arranged entoplasmic 

 alveoles near the micromere pole of each blastomere (PL II, Fig. 1 8) 

 In studying this stage with a low powder one soon notices that 

 the greater part of the ectoplasm has come down towards the 

 micromere pole (PI. II, Figs. 31, 22) 



Incidentally I might mention that the cell- wall between the 

 two blastomeres of Eucharis and CalUanira has a sieve-like appear- 

 ance (PL II, Figs. 22, 24, 27). In the latter form I was able to 

 see this peculiarity between two entoderm cells as late as the 

 gastrula stage. The fenestrated appearance is due to the lenticular 

 accumulation of a certain fluid as correctly observed by Chun ('80 

 p. 102) (cf. Fol '73 Tf. 24, Fig. 5). 



1 The surface of the bridge has r.idiatint' wrinkles. 



