STOLON FORMATION IN SPECIES OF TRYPANOSYLLIS. 425 
the spaces between which are occupied by (1) large oval 
nuclei with small scattered chromatin granules {mes. n.), 
(2) much smaller nuclei with a large intensely staining 
nucleolus (/.)• 
The body-cavity of the two penultimate segments is almost 
filled by leucocytes (Text-fig. 1 ; PI. 23 bis, fig. 12). These 
are of two types : either with an abundant investment of cyto- 
plasm, and laden with food material (/.), or with a mere super- 
ficial film of cytoplasm {V .). Both may be spherical or show 
amoeboid processes, and both possess small nuclei, with large 
intensely staining nucleolus. It is the existence of large 
numbers of nuclei of this type in the mesoblast, as noted 
abo've, that shows immigration of leucocytes to have taken 
place to a gieat extent. The larger type of leucocyte has 
undoubtedly, I think, a nutritive function, and may be ob- 
served in the meshes of the connective tissues, with the 
cytoplasm entire or partially disintegrated. But the smaller 
kind of leucocyte is too small to carry nourishment, and I am 
inclined to think that these wandering cells undergo a nuclear 
change, and become the actively dividing- cells of the meso- 
blast. In the latter stages, which have been examined by 
sections, no trace remains of this collection of leucocytes in 
tlie posterior segments — that is, they have all been ab.sorbed 
to add to the numbers of tlie proliferating cells or to nourish 
them for their task. 
VI II of d’. gem mi par a exhibits a further stage in 
development. As compai-ed with (1), it will be seen that the 
cushion of proliferation has increased in size, and projects 
beyond so as to overlap two segments in front of its point of 
origin. Posteriorly the growth of the stolons has been so 
marked as to press back the genital appendage from the 
position it should occupy as the prolongation of the stock, 
until it stands nearly at right angles to its former position. 
The number of rows of stolons is increased to about eleven, 
and it is seen that fresh rows are in process of being cut off 
fi-om a proliferating lip. 
d’lie preservation of this specimen is more favourable than 
