SOME OBSERVATIONS ON AGCINETARIA. 363 
some Infusoria (Biitschh, loc. cit., p. 1510) and Dendro- 
cometes (Hickson), are found to consist merely of local 
thickenings in the mesh of the nuclear network, and there- 
fore resemble karyosomes rather than true nucleoli. 
The micronucleus in the resting stage lies in a depression 
of the macronucleus, and consists of a membrane surrounding 
a clear area, in the centre of which lies a mass of feebly 
staining chromatin granules. 
Reproduction.—As regards reproduction, the process 
which Keppen termed external budding is referred to at the 
end of the section upon conjugation. The only method of 
reproduction observed in the Acineta papillifera from 
Hickling was by the formation of single internal ciliated 
buds. 
Keppen describes in addition to this for his form from 
Odessa, a process of multiple budding, but the figures that 
he gives are not convincing. One figure seems to me to 
show quite clearly that one so-called bud is simply a small 
individual with a fully developed stalk focussed through the 
large individual. The main features of the formation of the 
internal bud correspond with Biitschli’s description of the 
formation of the internal buds in Tokophrya quadri- 
partita. A small depression is formed on the apical sur- 
face of the acinetarian, which gradually widens so as to cut 
out a portion anterior to the macronucleus, the future bud. 
The free bud has a roughly cylindrical but slightly flat- 
tened shape (text-figs. 2 and 3). On its physiologically 
ventral surface it is covered with numerous rows of cilia. 
(Keppen speaks of 6—11 rows of cilia, but in the form from 
Hickling broad they seemed more numerous.) 
There is a contractile vacuole on the left side near the 
anterior end, with a small reserve vacuole near it. The oval 
macronucleus lies near the centre of the body, and in favour- 
able cases a micronucleus can be seen lying in a depression 
of the nuclear membrane. At first, after its escape, the 
embryo moves rather slowly, but a little later it moves 
rapidly through the water in characteristic sinuous curves, 
