6 1 4 GRIFFIN. [Vol. XV. 



The constriction of the cytoplasm which separates the polar 

 bodies does not commence until telophase, when the chromo- 

 somes are at the poles of the division figure (PI. XXXI, Fig. i6 ; 

 PI. XXXII, Fig. 19). At this stage there commences to appear 

 a small projection or knob of clear granular cytoplasm, entirely 

 devoid of yolk-spheres and containing the outer group of chro- 

 mosomes and the outer centrosome (or centrosomes). The knob 

 increases in height and with a deepening of the constriction 

 becomes balloon-shaped, connected with the egg by a narrow 

 cytoplasmic bridge. Often this constriction advances more 

 rapidly on one side, giving a slight obliquity to the polar body, 

 as in Limax (Mark, '81) and in the corresponding spermatocyte 

 division in Amphibians (Flemming, '87). With the severing of 

 the bridge the body rounds out, leaving the surface of the egg 

 rough and uneven, as described in Ophryotrocha (Korschelt, '95). 

 The second polar body arises in an essentially similar manner. 



Within the rising polar body the centrosomes and chromo- 

 somes take up an extreme distal position (PL XXXI, Figs. 15-18; 

 PL XXXII, Figs. 19, 20). In appearance and behavior the cen- 

 trosomes are in no way to be distinguished from those remaining 

 within the egg. Early divergence, which may take place while 

 the polar body is as yet represented by only a slight hummock 

 (PL XXXI, Fig. 15), followed by the appearance of rays, gives 

 rise to a minute amphiaster. Further divergence of the centro- 

 somes is accompanied by an elongation of the polar body, which, 

 in most cases, takes place tangentially, although sometimes, 

 doubtless owing to a mechanical rotation of the polar body, the 

 spindle lies with its axis in an egg-radius (PL XXXII, Figs. 

 21-25). 



The history of the chromosomes is, in all essential points, 

 but a repetition of that of those remaining within the egg. Soon 

 after the polar body becomes separated, or even while it is con- 

 nected with the egg (PL XXXI, Fig. 16), the line separating the 

 limbs of the daughter-V's becomes very clear. A little later 

 the limbs break apart at the angle and shorten up into sausage- 

 shaped bodies associated in pairs (PL XXXII, Fig. 22). An 

 equatorial grouping of these dyads follows upon sufificient diver- 

 gence of the centrosomes, but as the individual dyads tend to 



