20 BRITISH FRESHWATER RHIZOPODA. 
seemed evident that by mechanical irritation a “ reflex 
contraction” of the pseudopodia was produced, and, 
combined therewith, a secretion of a sticky coat on 
their surface, which caused the glass granules to 
adhere to the pseudopodia, and to be drawn in with 
them. 
By a series of experiments repeated upon other 
species of Difilngia, Verworn ascertained the great 
regularity of this process. When a Difflugia had 
extended its pseudopodia to a great length, and was 
groping about between the glass plates, it was irritated 
with a sharp needle; the same effect was then pro- 
duced with great exactness. The pseudopodia became 
tubercular, “and while previously no glass granules 
were adherent to them, these now clung firmly, and 
were slowly drawn into the shell. Specimens, the 
shells of which were partially removed, showed that the 
glass grains not only remained adherent to the surface 
of the protoplasm but were actually drawn into it. 
The same writer had subsequent opportunities of 
observing individual Diffiugqie undergoing division, and 
found that shell-formation in a young Difflugia accorded 
exactly with Gruber’s observations in the case of 
Kuglypha alveolatu. When the protruding mass of 
protoplasm from the old shell had attained approni- 
mately the normal size, he observed that a ball of glass 
granules had already, in part, entered the newly- 
formed half, in which the protoplasm with the finely- 
powdered glass showed a slowly-flowing movement. In 
amore advanced stage of division the protr uded proto- 
plasm had already assumed pretty nearly the form of 
the Difflugian shell (D. wreeolata), and the particles of 
glass had arranged themselves upon its surface. The 
new half seemed not yet to have a solid shell, but the 
glass granules were loosely fitted to one another. 
Upon separation from the parent the newly-formed 
individual was observed groping about in the water, 
with pseudopodia extended. The shell exhibited the 
characteristic form, but the pale bluish glass grains 
