290 WILSON. [Vou. IX. 
Bearing in mind the theoretical possibility of a gemmule 
originating from a single cell, I went to considerable pains in 
looking for any such indication. I could not convince myself 
with certainty that a gemmule ever was so formed, though I 
found cell groups such as a, Pl. XV, Figs. 10, 11, 13, looking as 
though they had been derived from single cells. Such groups 
though were very rare. 
Gemmules increase in size by cell-division. This is inferred 
at once from the large size of the cells forming the youngest 
gemmules as compared with the cells of older ones, Fig. 9. 
No karyokinetic figures were found, but the nucleus appears in 
several conditions, representing, no doubt, different phases of 
nuclear division. These different conditions of the nucleus are 
shown in Fig. 8’ (1, 2, 3, 4, 5), the arrangement of the figures 
indicating what I take to be the order in which the several 
phases follow one another. In stage 1, in which are all of the 
nuclei in the gemmules of Fig. 8, the chromatin forms a solid, 
usually angular, mass, and the nucleus is small. The mass of 
chromatin is relatively so large that very often it is difficult to 
make out the surrounding nuclear membrane, and the nucleus 
appears to be simply an angular mass of chromatin, as in the 
larger gemmule of Fig. 9. In what I take to be the second 
stage the nucleus is larger, and the chromatin forms a tangled 
skein lying in the center of the nuclear cavity. The smaller 
gemmule in Fig. 11 has its nuclei in this phase. In the third 
stage the nucleus is large, and the nucleoplasm very con- 
spicuous, the chromatin being distributed all round the 
- periphery. In the fourth stage there is no increase in size, but 
the chromatin is here collected at opposite poles. Examples 
of both these stages may be found in Figs. 9 and 11 —it is 
here seen that the several cells of a gemmule may be in very 
different stages of division. The remaining stage, which I take 
to be the one resulting from the act of division, is shown in 
Fig. 8’ (5). It is considerably smaller than 3 and 4, and the 
chromatin is confined to one side of the nucleus where it 
forms a thin but dense layer. Nuclei in this condition are 
shown in Pl. XIV, Figs. 13 and 14. These several conditions 
of the nucleus of the gemmule cell are all abundant and easily 
