6l2 GRIFFIN. [Vol. XV. 



At anaphase the ends attached to the traction-fibers are the 

 first to diverge, while the free extremities cleave together, pro- 

 ducing a more or less open V (PI. XXXII, Fig. 25). This 

 opens further, the two limbs become straight and then sepa- 

 rate, producing the appearance as though a single rod had just 

 divided transversely, precisely as Wilson has described in the 

 cleavage-spindle of Toxopnetcstes. The diverging halves maintain 

 a pretty constant length, and are as long as the daughter- F's 

 in the first polar telophase. At telophase the chromosomes 

 remaining within the egg pass into minute vesicles which, by 

 fusion or close aggregation, constitute the egg-nucleus. 



SUMMARY. 



/. By longitudinal fission and transverse segmentation of the 

 spircme-thrcad, there arise 12 {reduced number) ellipse-shaped 

 chromatin masses. 



2. These persist throjighotit the growth period of the egg. 



J. During prophase they concentrate into crosses, the arms of 

 which are tight loops. 



.f. In the first polar division, these are drawn out again into 

 ellipses zvhich divide to form daughter- Vs {equation division). 



5. The V's break apart at the angle in the second polar divi- 

 sion (reducing division). 



b. In Fertilization and Cleavage. 



In general, the sperm enters nearer the vegetative pole, though 

 it occasionally penetrates above the equator.' After entrance 

 it increases enormously in size, but remains not far from the 

 surface as a large black sphere within a clear area (PL XXXI, 

 Fig. 12 ; PI. XXXII, Fig. 19). By second polar telophase, 

 roughly speaking, it becomes vesicular (PI. XXXII, Fig. 26) 

 and ultimately gives rise to a fine reticulum like that of the egg- 



1 In one or two cases a sperm (probably a supernumerary one) had entered at 

 the animal pole, near the outer aster of the first polar figure. A similar fact has 

 been reported by Foot ('95) in Allolobophora, and Kostanecki and Wierzejski in 

 Pkysa. 



