SMALLWOOD : MATURATION OF HAMINEA SOLITARIA. 283 



In Figures 32 and 32a the first polar cell has been formed ; and the egg 

 centrosome, now metamorphosed into the second maturation spindle with 

 its two minute ceutrosomes, is seen lying nearly at right angles to the 

 chief axis of the egg. The chromosomes within the egg are very small 

 and lie ovatside the spindle, their relation to the spindle being indicated 

 in Figure 32a. The crossing of the rays from the two asters is prominent 

 on the side of the spindle nearest the animal pole of the egg. Inter- 

 mediate stages between the conditions represented in Figures 30 and 

 31a have been observed, but they were unfavorable for reproduction. It 

 may be stated, however, that the centrioles are connected by a central 

 spindle, and that both the centroplasm and its limiting boimdary, seen 

 in Figure 30, disappear ; that the rays increase in length ; and that the 

 sphere substance becomes indistinguishable from the surrounding cyto- 

 plasm, so that it has not been possible to establish any direct connection 

 between the old sphere and the spheres belonging to the second mitotic 

 figure. The successive positions assumed by the spindle, until it comes 

 to be radial and to have one pole at the surface of the egg, are seen in 

 Figures 32-36. In the case shown in Figure 34, the spindle evidently was 

 formed more deeply in the egg than in the case of Figures 32 and 33. 



The separation of the daughter chromosomes in the first polar cell is 

 shown in Figure 32a.^ The centrioles are very faint, and around each 

 there is a diffusely stained region in which a few rays only can be seen. 

 There can be distinguished in this polar cell 28 chromosomes, 14 in each 

 half. It is probable that the other four lie beneath some of those counted. 

 The derivatives of the first polar cell in Figure 53 (Plate 8) show in an 

 interesting manner the persistence of the interzonal filaments, and (what 

 has been observed for these derivatives in this one case only) the presence 

 of a small " midbody." 



The centrosomes con.'cted with the second maturation spindle grow 

 each from a small granule, as seen in Figure 31 (Plate 6), to a relatively 

 large body composed of centroplasm and one centriole, as seen in Figures 

 33, 34, 36 ; but this enlarged condition is preceded by one in which the 

 centrosome has an irregular form, as represented in Figures 32 and 35. 

 The centrosome here seems to be elongated in a direction transverse to 



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^ An objection to considering tlie cell shown in Figures 32 and 32a, the polar cell 

 of the egg shown in Figure 32, is tlie fact that it is more advanced toward an ap- 

 proaching division than the egg itself; but this interpretation is confirmed by the 

 relative positions of the two, and by tlie stage of development of the eggs associated 

 with this one. 



