Timhcrlahe — Swarm-Spores of Hydrodidyon. 499 



slightly elongated with one end quite small and drawn out into 

 a blunt point, that is directed toward the cleavage plane (Figs. 

 29 and 30). In other cases the nuclei are more elongated and 

 the two ends are of tlie same size. Such forms may be con- 

 stricted in the equatorial region so as to suggest strongly that 

 direct division is taking place. (Figs. 21a, 22, 23.) Both of 

 the above mentioned forms of nuclei generally occur together 

 in the same cell. (Figs. 21-23). They may in turn be associ- 

 ated with those that are more definitely amoeboid or angular in 

 outline. The size of such nuclei varies very strikingly 

 (Compare Figs. 6, 21, 34 and 44). In figures 6, 34 and 35 

 are shown the extremely large size that the elongated amoeboid 

 and angular nuclei may reach. Such unusually large nuclei 

 may occur in apparently any stage of cell life, although my 

 preparations have not sIiOAvn them in ciliated swarm spores. 

 Still they occur in the cells in which the cleavage is complete 

 (Figs. 34, 35), as well as in the cells of very young nets (Fig. 

 44). By comparing figures 43 and 44 a very good idea may be 

 obtained as to the relative size that such nuclei may attain. 

 Both figures are drawn according to the same scale of magni- 

 fication. 



In all of the irregular shaped nuclei the contents generally 

 present the same appearance as in the other nuclei in the cells 

 in which cleavage is taking place. 



The distribution of the nuclei presents some interesting 

 phenomena. Those described above as typical resting nuclei 

 are generally quite evenly distributed throughout the cytoplasm 

 at points equidistant from one another (Fig. 3). The number 

 of such nuclei that may occur in a given area of the protoplasm 

 varies considerably. As Klebs pointed out, cells are often 

 seen in which the nuclei are much too numerous to have swarm 

 spores of the normal size formed in the cell with a single nu- 

 cleus to each spore. But the assumption that a fusion of nu- 

 clei occurs in such cases before or during cleavage is not 

 at all necessary, for there is no evidence that such cells are go- 

 ing into cleavage stages wuthout further growth. Even if 

 they are in the same net in which some of the cells are forming 

 spores they may not, as I shall show" later, themselves undergo 



