18 



Circumference ihrougli its fibres becoming longer and bending out- 

 wards. At the end of karjokinesis the spindle moves away and 

 often turns so that its longitudinal axis makes an angle with that 

 of the cell. The daughter-nuclei move against the chromatophores 

 which divide into two. Thej take up a position between the new 

 chromatophores of the daughter-cells. The transverse wall develops 

 in the same way as in Spirot/j/ra. It ai-ises at tiie longitudinal wall 

 and grows inwards until the cell is divided into two. The division 

 of the chromatophores generally occurs after celhdar division, but it 

 is not limited to the latter, for cells with 3 or 4 chromatophores are 

 sometimes met with. 



Sunnnari/ of results. 



1 . In Ziignema cruc'uitnm as in Spimgyra the nucleolus has a peculiar 

 structure. It contains a l bread with two thickened ends or indeed 

 two corpuscles, which are united by a thinner thread. 



2. The nucleolus dissolves when karyokinesis begins. I cannot say 

 with certainty whether, as in Spiro(/i/ra, there remain behind morpho- 

 logical elements, which jilay a part in karyokinesis, but I consider 

 this piobable. 



3. There is no perinucleolar cavity (cavité périnucléolaire of 

 EscoYEz) in living specimens of Zygnema cruciatum. 



4. In Zygnema the chromosomes, short threadlike pieces or lumps, 

 arise from the nuclear network, as Escoyez also assumes and not 

 from the nucleolus, as Miss Merri.man imagines. 



5. During karyokinesis the chromosomes remain continually united. 



6. In Zygnema cruciatum the chromosomes do not form tetrads 

 as i\liss Merriman claims to have established in this genus. 



7. The nuclear membrane dissolves, but this is not accompanied 

 by a penetration of the spindle-fibres into the nucleus or nuclear 

 cavity. 



8. The halves of the nuclear-plate arise, as Escoyez also assumes, 

 through longitudinal splitting of the nuclear-plate, and not through 

 the grouping of the chromosomes in two parallel planes without 

 splitting, as Miss Merriman maintains. 



9. In Zygnema cruciatum tiie nuclear plate is disc-shaped and not 

 annular as Miss Merriman and Escoyez believe they have seen in 

 Zygnema. 



10. The network of the daughter-nuclei develops from the halves 

 of the nuclear plate. 



11. The nucleolus is formed Iw the coalescence of many smaller 

 ones to a single body. 



