MATtJRATK)N OF OVUM IN ECHINUS ESCULENTUS. 201 



size. In reality^ just like the earlier bodies, they are short, 

 somewhat curved rods, Avith dilated extremities placed side 

 by side. Those at the outer pole pass iuto the first polar 

 body, and those remaining in the egg persist, enlarge 

 somewhat, and pass otherwise unchanged into the second 

 polar spindle. Sometimes during the metakinesis the second 

 longitudinal split is not so evident, and then long drawn 

 out threads ai'e seen, the double nature of which is difficult 

 to make out. Ultimately, however, the two halves separate 

 in the anaphase exactly as in other cases. Exactly similar 

 figures have been described by quite a number of observers 

 in other forms, for instance, and especially distinctly, by 

 Klinckowstrom (1897), Francotte (1897), Van der Stricht 

 (1898), Griffin (1899), Gathy (1900), but, as I shall describe 

 in the sequel, their interpretation has been different, and 

 leads to very diti'erent theoretical conclusions. The transi- 

 tion between the first polar and the second polar spindle is very 

 rapid, so that the number of sections found in this stage is 

 relatively few. 



The little compound chromosomes are drawn into the 

 equatorial plate of the second spindle (figs. 23 and 24), 

 and there diffei'ent appearances are seen, according to the 

 plane of the section. In fig. 24 we have apparently little 

 tetrads, which are really the lobed ends of the small, slightly 

 curved chromosomes. In fig. 25 again the rods are seen 

 lying back to back. These rods I have every reason to 

 believe, from the various figures I have drawn, open out just 

 as in the first spindle, only there is no second longitudinal 

 split, and therefore the division is homotypical. A single 

 preparation rather suggests that the rods may sometimes 

 be simply separated along the plane of cleavage. It may 

 well be that both methods are adopted, according to whether 

 the body lies radially or tangentially to the spindle. The 

 result is the same ; the separation is effected in the plane 

 of cleavage established in the anaphase of the first division. 



Similar figures in the second division have been described 

 by the authors above mentioned, and in other instances. 



