smallwood: maturation of haminea solitaria. 287 



first polar cell has apparently begun, even though the chromosomes are 

 still near the equator of the spindle. 



It will be seen by comparing Figures 38, 39, and 49, that the axis 

 connecting the new centrioles has no fixed direction in relation to the 

 axis of the first maturation spindle. I have never seen a polar cell 

 resulting from this second or indirect process of maturation while it 

 was in the act of being constricted off, — a stage corresponding to that of 

 the direct process illustrated in Figure 30 (Plate 6) ; but the stages 

 immediately before and immediately after the foi'mation of the first 

 polar cell by the indirect method are abundant. 



The deep centrosonie in Figure 38 may be looked on as a stage 

 of long duration, because the eggs found in this condition far exceed in 

 number those exhibiting conditions that precede or follow it. The 

 changes following this condition take place rapidly. The first indica- 

 tion that the centrosome has entered on another phase is the occurrence 

 of small breaks in its boundary (Figs. 39, 40). Immediately after this 

 boundary begins to break down, faint indications of a new accumulation 

 of cortical substance around the centrioles appear ; usually this is first 

 seen between the centrioles and the end of the centrosome ; however, 

 it may appear simultaneously on all sides of the centrioles. With the 

 appearance of this new cortical layer there are formed rays which at 

 first are short and few in number, as in Thysanozoon (Van der Stricht, 

 '98). As soon as the rays are formed, the term " centrosome " should, 

 according to our definition, be applied to the body which hitherto has 

 been termed " centriole." The centrosomes, thus formed by the enlarge- 

 ment of the centrioles, now begin to separate from each other ; the 

 central spindle (Jus. c.) becomes more conspicuous, and the cortical layer 

 increases in extent (Figs. 41-45). The growth of this central spindle is 

 interesting ; it is limited laterally by a well-marked boundary ; within 

 this there are several fibres extending from one centrosome to the other 

 (Plate 7, Figs. 42, 44 ; Plate 11, Fig. 74). As the spindle increases in 

 leugth, the outer boundary increases in distinctness and the contained 

 fibres become less evident ; this diffbrentiation continues until the fibres 

 become very faint and at the same time anastomose (Fig. 45) with one 

 another. This gives them a branched appearance, similar to the con- 

 ditions found in Diaulula by MacFarland. 



The next stage is represented in Figures 46 (Plate 7) and 76 (Plate 

 ll). There extends between the two asters a conspicuous fibre. This 

 is probably the remnant of the central spindle ; if so, it has increased in 

 staining capacity. It has an irregular, wavy course ; the outer end 



