290 WILSON. [Vol. 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, PI. XV, Figs. 10, 1 1, 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' (i, 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 i, 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. 1 1 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 PI. XIV^, Figs. 13 and 14. These several conditions 

 of the nucleus of the gemmule cell are all abundant and easily 



