162 The Significance of Sex. [ Feb, 
centres on either side of it, or it may, like a pseudopodium, reach 
out and obtain a fresh connection with a neighbor. This is ad- 
mirably illustrated in Fig. 123. In this way it is that a reticulum 
can be transformed into a mitom or a fibre. The observations of 
Rabl and of Retzius on the formation of the mitom become 
intelligible. By the attraction of the hyaloplasm along definite 
paths, and their separation along others, we may also see how a 
nucleus arises in a cell, as in Fig. 2. By mutual attraction the 
microsomata fuse. Why they segment may be explained by 
assuming that certain gemmules or societies of gemmules differ- 
entiate from the others and serve as governing centres, about 
which the rest flock. Individuality arises in this way everywhere. 
The cause of union between two units of like order, which con- 
stitutes sexual union, is not so apparent. We find this occurring 
only where a slight difference has arisen, so that, Lankester says, 
“they may mutually gain each other’s experience.” At bottom 
all the phenomena of the cell-life may be referred to attrac- 
tions, and through its action the reticulum becomes the organ of 
movement. 
There is considerable evidence that successive cell-divisions 
differ in their karyokinetic phenomena. We know that the num- 
ber of karyosomata in the segmenting-egg are fewer than in the 
tissue-cells, and that they are shorter. There must be a change 
somewhere. But in gametogenesis two successive generations 
may differ, as can be seen by Figs. 123 and 124. We may start 
in gametogenesis with direct division, pass on to generations pro- 
duced by budding or by stenosis, and finally reach the complex 
phenomena of the segmenting embryo. We know only a little. 
ut this. Our knowledge compares with what we should 
know, as the knowledge of zoologists, before embryology, com- 
pares with their present knowledge. When we reflect that we | 
must observe cells in all periods of their life and all the genera- 
tions of cells as they differentiate, and we must do this for all 
the different animals, and the results must be corroborated by 
different observers, morphologists need not quarrel for lack of 
room nor sit idle for lack of work. We can also understand why 
is is such a mysterious phenomenon.  Ce//-division 
= must be r understood onlegeutically and PS 
_ (To be concluded. ) 
