No. I.] 



MYZOSTOMA G LAB RUM. 



309 



at some distance from the male. Their appearance is that of 

 Fig. 7, where the first traces of a spindle are forming between 

 the two centrosomes — which I take to be the two originally 

 stationed at the inner pole of the second polar body spindle — 

 and faint traces of radiations can be detected in the surround- 

 ing archoplasm. These radiations soon come out with startling 

 clearness, and the centrosome of each astrosphere immediately 

 divides (Fig. 8). Occasionally there are three centrosomes in 

 each astrosphere like those figured by Heidenhain.^ This stage 

 and the ones which follow in the formation of the first cleavage 



Fig. 7. Fig- 8. 



spindle have been misinterpreted by Fol.^ TJie centrosomes 

 are not fusing in pairs, but already dividing in anticipation of 

 the 4-ceU stage of the ovum. 



The two pronuclei are very soon brought together, as in 

 Fig. 9, and the first cleavage spindle is established. In Myzos- 

 toma this spindle does not conform to O. Hertwig s law? but 

 always lies at right angles to the longest axis of the often very 

 narrow protoplasmic pillar of the egg. The walls of the pro- 

 nuclei are pushed in irregularly by the spindle fibers in much 

 the same fashion as was the wall of the germinal vesicle in an 

 earlier stage. They ultimately fade away, and the chromatin, 



1 Neue Untersuchungen iiber die Centralkorper, 1894, Taf. XXVI, Fig. 27. 



2 Le quadrille des centres. Arch, des Sciences Phys. et Natur., t. XXV, No. 

 du 15 Avril, 1891, Figs. 8-10. "^ Zelle und Gewebe, p. 175. 



