STRUCTURE AND LIFE-HISTORY OF COPROMONAS SUBTILIS. 89 
soon begin to writhe about (figs. 4 and 5). As they increase 
in length they exhibit the characteristic movements of these 
structures, and the dividing organism again becomes motile. 
A cleft has meanwhile appeared between the bases of the 
flagella. It extends backwards slowly, cutting the reservoir 
in two as it does so. The nucleus becomes completely parted 
into its two daughter-products, and by the cleft gradually 
extending to the posterior of the body two daughter- 
individuals are formed, and subsequently break away from 
one another (see figs. 9.and 10). The whole process lasts 
twenty minutes or thereabouts. 
The foregoing is a general account of the way in which 
longitudinal division is effected. I will now describe in 
detail the manner in which the various organelle of the 
monad are doubled in the formation of daughter-individuals. 
Details of division.—These must be considered in the 
case of (4) the nucleus, (8) the flagellum, (c) the cytostome, 
(p) the reservoir or contractile vacuole. 
(A) The nucleus.—(Pl. 4, figs. 6-10; Pl. 5, figs. 34-40). 
Nuclear division is effected by a kind of amitosis. It thus 
differs from the phenomenon which has been observed in all 
other members of the order Huglenoidina which have been 
accurately investigated. (See infra, p. 104). 
In the living organism no details of division can be seen 
in the nucleus. It can be seen to elongate, and become con- 
stricted into two—as shown in figs. 1-5, Pl. 4—but beyond 
this nothing can be made out. However, in preparations 
stained with iron-hematoxylin, and carefully differentiated, 
the following details of division may be observed (see Pl. 
5, figs. 34-40). Before division the nucleus consists—as 
already noticed—of a central chromatin-containing body, 
(‘ Innenkérper ”) surrounded by a clear, non-stainable zone 
(“ Kernsaftzone ”) bounded by the nuclear membrane. 
Achromatic strands cross the clear zone, connecting the 
nuclear membrane with the central body (fig. 34). In strongly 
- differentiated iron-hematoxylin preparations the central body 
appears to consist of an achromatic substance in which 
vou. 52, PART 1.—NEW SERIES. a 
