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PROGRESS OF MICROSCOPICAL SCIENCE. 
matter. These transparent masses are remarkable for the spontaneous 
changes of form and other quasi-amoeboid movements which occur 
among them. 
Dilute infusions of meat cause a similar elfect, astonishing 
quantities of transparent matter being produced. 
It has been shown that the filaments are protoplasmic bodies, 
containing a large quantity of resinous matter. The question next 
arises, with what process in plant-physiology is the protrusion of 
filaments homologous ? 
The leaf-glands of the teasel are similar in general structure to 
many glandular hairs which produce resinous and slimy secretions, 
and, like these glands, they contain bright drops of secreted resin 
lying in the centres of the gland-cells ; they also resemble many 
glandular hairs in being often capped with accumulations of secreted 
matter. Now these accumulations stain red with alkanet, yellow with 
iodine, and are largely soluble in alcohol ; that is to say, they consist 
of substances which have the same reactions as the filaments. There 
is, in fact, no doubt that the caps of resinous matter on the teasel- 
glands arc produced by the accumulation of dead filaments. According 
to this view, the act of protrusion is essentially a process of secretion : 
the resin issues from the gland-cells, mingled with a certain amount of 
true protoplasm ; and it is only from the death of the living or 
protoplasmic part of the filaments that the resinous accumulation 
results. This view of the act of protrusion corresponds with the 
theory of secretion held by some physiologists, viz. that secreted 
matter is produced by the dissolution or death of protoplasm — that, 
for instance, the oil in a fat-cell is the result of the disintegration of a 
plastid or individualized mass of protoplasm formed in the cell by 
endogenous cell-formation. 
The protrusion of protoplasmic filaments from the glands of the 
teasel appears to bear an obscure relationship to the phenomena of 
“ aggregation ” in Drosera and several other plants. In both processes 
we have homogeneous, highly refracting protoplasmic masses, which 
undergo amoeboid movements, and are in some unknown way con- 
nected with the absorption of nitrogenous matter. In Drosera the 
protoplasmic masses remain within certain cells ; in Dipsaeus they are 
protruded through the cell-wall. 
When we begin to inquire as to the function of the filaments, the 
answer seems at first to be sufficiently plain ; but this is very far from 
being the case. Tho connate leaves of the teasel form cup-like 
cavities, which become full of rain and dew in which many drowned 
insects accumulate. The glands at the base of the leaves are thus 
exposed to a highly nitrogenous fluid. And since such fluids are 
known to produce a remarkable effect on the filaments exposed to them, 
it seems probable that the filaments are in some way connected with 
the assimilation of food material. It seems probable that, either with 
or without the assistance of their filaments, the glands do absorb some 
nitrogenous matter ; for changes of their cell-contents occasionally 
occur which can only thus be interpreted. But on account of the 
rarity and uncertainty of these aggregation changes within the glands, 
