4o8 TREADWELL. [Vol. XVII. 



"intermediate girdle" cells, which occupy the spaces between 

 the arms of the cross (PI. XXXVI, Fig. 8). 2. The division 

 of the primary trochoblasts (PI. XXXVI, Fig. 9). j. The divi- 

 sion of the second group of ectomeres (PL XXXVI, Fig. 10). 

 At the 32-cell stage, although well-marked size differences have 

 appeared among the cells, the quadrants are still radially sym- 

 metrical, and it is impossible, by any differences in size or 

 arrangement of cells, to distinguish them. The polar furrow 

 retains its original direction and enables us to distinguish 

 between the two cleavage planes, but no other orientation 

 mark appears. 



At the 32-cell stage the polar globules, which until this time 

 have occupied a position at the upper pole of the egg lying 

 on the inner face of the rounded ectomeres, pass into these 

 latter cells, where they may be seen as small, deeply staining 

 bodies, lying in the protoplasm of the cell (PI. XXXVI, 

 Fig. i\, pg, and Text-Fig. 4). This position they retain for 

 some time. There seems to be no regularity in the process, 

 the bodies sometimes passing into one and sometimes into 

 another of the large cells. Similar observations have been 

 recorded by Mead (No. 22) in Lepidonotus, where, also in the 

 32-cell stage, the polar globules pass sometimes into one, 

 sometimes into another of the cross cells, or they may even 

 be found in the segmentation cavity ; and in Chaetopterus, 

 where the polar globules are ingested by the rosette cells. 

 Grobben (No. 10) finds in Cetochilus that at least one polar 

 globule wanders into the segmentation cavity, where it, pre- 

 sumably, is absorbed. Hatschek (No. 11) in Eupomatus, and 

 Eisig (No. 8) in Capitella, have described a similar fate for the 

 polar globules. (See p. 417.) 



Thirty-two to Sixty-four Cells. — The 64-cell stage is " actual " 

 in Podarke, and is reached by the leiotropic division of each of 

 the thirty-two cells. Here, as before, there are three well-marked 

 subdivisions. /. Thirty-two to forty cells. The fourth group 

 of micromeres arise at the lower pole (PI. XXXVII, Fig. 13), 

 and four very small cells, the apical rosette, are divided off from 

 the large cells at the upper pole (PI. XXXVI, Figs. 11 and 12). 

 It is important to note that the cells of the fourth quartette 



