242 M. M. Metcaur 
divisions occurring at once (Q). Sometimes the division furrow begins 
in the middle of the body, instead of at the edge, and spreads to 
the edge (Y). Tdnnices (1899) has described exactly parallel phe- 
nomena in the irregular divisions of O. ranaruwm in the spring. 
Were the divisions of the body always as regular as ZELLER 
describes, one would be tempted to compare them with the regular 
divisions of an egg, in which each division plane has a definite and 
predictable direction. Vegetative division in most Ciliata is trans- 
verse; in the Flagellata it is longitudinal; in Opalina it is generally 
longitudinal, sometimes transverse, and, in the multinucleated flattened 
species, sometimes irregularly oblique. 
Time of appearance of the new nucleolus. 
We have already seen that the nucleolus in the parent nucleus 
does not divide, but remains in one of the daughter nuclei, the other 
daughter nucleus acquiring a new nucleolus. This new nucleolus 
appears near the pointed end of the nucleus, where it narrows to 
the thread which connects it with its sister nucleus (Fig. 72, Pl. XIX). 
The new nucleolus does not appear in the daughter nucleus until 
the chromatin ribbon is ready to break up, or has already broken 
up, into separate chromatin masses. It increases and is of full size 
by the time the new spindle for the next division begins to form. 
Differences between the two nuclei. 
Very often the two nuclei are not in exactly the same stage 
of mitosis. Frequently one half of the dividing nucleus will have 
its chromosomes all distinct, while the other half shows them be- 
ginning to unite by means of band-shaped pseudopodia (Fig. 58, 
Pl. XVIII; 34, Pl. XVI); or one nucleus may show a complete 
chromatin ribbon while the other has its chromatin ribbon already 
broken into a number of pieces (cf. Fig. 37, Pl. XVI, in which one 
nucleus shows fourteen (?) chromatin masses, while the chromatin 
ribbon of the other nucleus has not yet completely divided). In 
very many cases in nuclei which are forming and casting off the 
chromatin spherules, soon to be described, one sees these spherules 
larger in one nucleus than in the other, or already separated from 
the chromatin masses in one nucleus but not in the other. In ab- 
normal nuclei of animals kept too long outside the host, there are 
often differences between the two nuclei (Fig. 95, Pl. XX1). Gener- 
