236 
Malcolm E. Stickney 
dense and strongly granular protoplasm. No nuclear reticulum ! 
could be made out in the resting nuclei, athough the nucleolus i 
appears sharply defined as a deeply staining granule, apparently | 
spherical and homogeneous in resting nuclei, and distinctly lobed 
in those which have recently divided (fig. 5). 
The nucleus evidently divides with great rapidity in cells grow- i 
ing under favorable conditions, for while large numbers of divid- | 
ing cells were found, and all stages in the reproduction of the colo- | 
nies were freely represented, showing that nuclear division must | 
have been taking place abundantly, only two nuclei in a state of || 
actual division were found in the preparations studied. These i| 
division figures were both in late anaphase, with a clearly marked ! 
central spindle and chromosomes well drawn back toward the ( 
poles. The chromosomes appeared as very short rods, twice as || 
long as wide, and while their number could not be made out with | 
certainty, it was small, evidently in the neighborhood of six or j| 
eight. No centrosome could be distinguished, but the presence of I 
the chromosomes in the polar regions would necessarily make it ( 
difficult to differentiate a separate centrosome body. || 
As has been noted, the cilia are four in number (fig. 2), and are |i 
nearly three times the length of the cell. They arise from a j 
wart-like protuberance at the anterior end of the cell — the so- | 
called ‘‘mouth-piece.’’ In one preparation studied delicate fibers | 
appeared extending back from the mouth-piece, between the vacu- j 
oles, to the vicinity of the nucleus. As these filaments were made |i 
out in but a single preparation it would be somewhat hazardous to j 
attempt to identify them with similar structures of Dangeard^ || 
or Timberlake.^ j| 
According to Stein’s account reproduction takes place in Spondy- j| 
lomorum essentially as in Pandorina and other members of the : 
Volvox family, that is, by a division of the protoplast within the j 
mother wall into sixteen daughter cells, which escape by the rup- I 
ture of the enclosing membrane. The division, however, is not an { 
internal one, but there is in every case a complete cleavage of the !| 
entire cell. Hence there is no “escape from the mother cell” on [i 
the part of the daughter colony, since the daughter colony was 
^ Dangeard, P. A. Etude sur la structure de la cellule et ses functions, Le Poly- jj 
toma uvella. Le Botantste^^w. 1901. I 
* Timberlake, H. G. Swarm-spores of Hydrodictyon. Transactions of the 
Wisconsin Academy of Sciences, 13: 486-515- IQOI. j 
