1091 
The thicker parts are comparable to chromosomes. Well-formed 
chromosomes, such as are met with elsewhere in the vegetable kingdom, 
do not occur in Eunotia. The nuclear wall dissolves and conse- 
quently -the nucleus loses its sharp outline; the nucleolus also 
gradually disappears. 
To this point karyokinesis in Eunotia presents nothing peculiar, 
but tbe further course of the process is wholly different from that 
in higher plants. In the centre of the mass of protoplasm in which 
the nucleus is found, the central spindle can soon be distinguished. 
It is a strand of protoplasm of which the outer ends are turned 
towards the two shelis. At first I could distinguish the central spindle 
as a short rod embedded in the protoplasm, but in later stages of 
karyokinesis I observed it extending right across the whole mass 
of protoplasm ; the two ends were seen to be club shaped and thic- 
kened. | was unable to study the origin of the central spindle, 
since the amount of material at my disposal was insufficient. 
The nuclear network contracts around the central spindle, and 
in this way the ring shaped nuclear plate is formed in Eunotia. 
The latter divides into two halves which are likewise annular and 
separate from each other along the central spindle, until they are 
finally quite at the spindle ends. Together with this, there occurs 
division of the mass of protoplasm in which the nuclear plate lies. 
It divides into two parts, which send out strands of protoplasm in 
different directions just as did the whole mass and at first they are 
also connected with one another by strands of protoplasm. The 
whole figure very much resembles the diaster stage in higher plants, 
although I have never been able to distinguish a nuclear spindle. 
Meanwhile the primary division-wall has developed; it broadens 
out more and more and approaches the nuclear figure} the proto- 
plasmic links between the halves of the nuclear plate and the central 
spindle are divided into two. The central spindle disappears. The 
daughter-nuclei are now very close against the division-wall, then 
separate again from each other, move into the neighbourhood of the 
epitheca and hypotheca and finally take up a position in the middle 
of the daughter-cells. 
With the development of the annular halves of the nuclear plate 
into daughter-nuclei the same phenomena appear as in the formation 
of the nuclear plate from the resting nucleus, but in reverse order. 
The rings divide into lumps or short thread-shaped pieces which 
remain connected with each other by fine threads of protoplasm ; 
the division proceeds to a point at which the nuclear network 
agrees again with that of the resting nucleus. In fully-developed 
