344 
F. E. Fritsch. 
between the protoplast and the envelope. I am inclined to 
think, however, that such cases may mark incipient division. In 
plasmolysed individuals the cilia are drawn back with the contracting 
protoplasm and their lower portions are readily recognisable on the 
inner side of the envelope (Fig 1, B, C); this shows how freely they 
can move within the cilial apertures. It should be added that in a 
few cases the space between envelope and protoplast was occupied 
by a certain amount of granular matter (Fig. 1, F). 
With reference to the reproduction of Isococcus I am unfortu¬ 
nately able to say but little, all cultures with the object of elucidating 
certain points having hitherto proved unsuccessful. Large numbers 
of stages like those shown in Fig. 1, H-J were met with and I have 
no doubt that these represent the ordinary method of reproduction 
of the organism by division. This process appears invariably to take 
place in the resting condition and to be accompanied by a gradual 
widening out of the envelope; in early stages, before the latter has 
increased much in size, the small collars surrounding the cilial 
apertures are still clearly recognisable (Fig. 1, H), but in later stages 
these details of differentiation are lost. In all those cases, in which 
the point could be definitely settled, the plane of the first division of 
the protoplast was longitudinal (Fig. 1, H). Most commonly two 
successive divisions appear to occur, so that four individuals were 
found within the enlarged envelope of the mother (Fig. 1, 1); more 
rarely, cases were observed in which only two individuals had 
been produced, whilst only once was division into eight noticed. 
When division into four takes place the daughter-individuals are at 
first ranged parallel to one another, although later their orientation 
becomes more irregular ; in the single case noticed of division into 
eight, the arrangement of the individuals gave no clue to the direction 
of the third division-plane. In the smallest forms exhibiting division 
into two, the envelope measured 26/x in diameter, i.e., agreed in 
dimensions with the largest of the free-swimming individuals ; the 
daughter-individuals in this case measured 16/a long by 13/x wide. 
In many of the division-stages observed however the envelope was 
much wider, attaining to as much as 80/x in diameter. 
In many of the stages observed, the individuals within the 
mother-envelope were already fully developed, exhibiting all the 
characteristics described above (Fig. 1, I), and it would appear as 
though for the most part liberation does not take place till this 
condition is attained. In a few cases (all observed in the late 
afternoon) the daughter-individuals were seen to exhibit a slow 
movement to and fro within the mother-envelope, the cilia of one 
