keeps the form of a quadrant. The details of these changes 

 can be traced only in the transparent ova of slugs. When the 

 yolk takes the biscuit form, the nuclei are elongated 

 (Figure 40, 26); following this the elongation and twisting 

 of the yolk globules themselves takes place (Figure 40, 26a) . 

 The twisting in Lymnaeus stagnalis and slugs begins in one 

 globule earlier than in the other (Figure 39, 27), however, 

 soon after this difference smoothes out. The boundary between 

 the globules of division, corresponding to the first fissure, 

 is at first straight (Figure 39, 27), and then becomes 

 curved (Figure 39, 29, 30), and the yolk globules are situated 

 crosswise in two planes. 



The processes taking place in the nuclei were described 

 by Warnek as follows: "The membranes of the nuclei disappear, 

 the nuclei elongate, take an oval biscuit-shaped form, then 

 bulge out, and finally each nucleus from the beginning of 

 the division of the yolk globules is divided into three parts. 

 From these parts of the nuclei only four are present in the 

 globules of the division, and two gradually disappear in 

 the fissures between the globules. The four nuclei at first 

 have the form of a comet. When the division of the yolk 

 globules is finished, the CAUDIFORM processes of the nuclei 

 extend and the nuclei again acquire the rounded form" 

 (pp. 146 - 147). The three parts into which, according to 

 Warnek, each nucleus is divided correspond to the two daughter 

 nuclei and to the achromatic figure of mitosis situated 

 between them. 



The final step of the third stage is the formation of 

 the membranes around the nuclei and subsequent turning of 

 the cross-shaped globules of division. Two of them are in 

 contact with each other on the dorsal side, and the other 

 two on the ventral (Figure 39, 34) . Between the yolk globules 

 a rhomboid space appears during which this is especially clear 

 in Limax. 



THE FOURTH STAGE . At the beginning of the fourth 

 stage the nuclei in the yolk globules of Lymnaeus stagnalis 

 again become unnoticeable from outside. During the crushing 

 out of ova it is possible, however, to see the changes 

 occurring in the nuclei, which, as in the previous stage 

 do not take place at the same time. In Figure 39, 36a it is 



552 



