LIFE-HISTORY OF BUCEPHALUS HAIMEANUS. 651 
nuclear contents are more coarsely granular. These contents 
in a later stage are seen gathered together in two masses, 
the large nucleus of the germ-cell having, in the meantime, 
moved to the opposite periphery of the cell. In stages which 
I believe to be still older, a second small cell has made its 
appearance, and still later there are three, two of which seem 
to be the result of division in the first cell (fig. 15, c). 
Reuss (41, 1903) has seen a similar phenomenon in the 
sporocysts of Distomum duplicatum, and has interpreted 
these small cells as being of the nature of polar bodies. 
Haswell (238, 1903), describing germ-cells of Echinostomum 
sp., has noticed in the vicinity of the ovary (Keimlager) a 
number of cells which have deeply staining homogeneous 
nuclei, although he has never seen a stage similar to that 
described by Reuss or by me. In this connection Haswell 
says: “If these are not of the nature of polar bodies, it 
seems difficult to account for them.” 
Tae SEGMENTATION OF THE GERM-CELL. 
The subsequent behaviour of the germ cell is similar to 
that of a segmenting egg. 
It has been impossible to observe the actual processes of 
segmentation in living material, the opacity of the wall of 
the sporocyst rendering observations unsatisfactory. In 
entire mounts of preserved material and in sections the 
selection of succeeding stages depends only upon patient 
search. 
The division of the cells is mitotic. Although it has been 
impossible to make out the process of spindle formation in 
living material, and although sections but rarely indicate 
such a process, the evidence furnished by these exceptional 
instances seems clear (fig. 21). 
The germ-cell in its first division is cut into two cells of 
nearly equal size, one being somewhat larger than the other 
(fig. 15, c). Jn the second division the smaller of these two 
