708 MICROSCOPY. 
The animalcule of the sponges is described, in its passive form, 
as “a minute globular cell, apparently filled with ‘granuliferous 
plasma, bearing a nucleus and two contracting vesicles, provided 
with a rostrum or projecting cylindrical portion supporting a delicate 
fimbriated collar, in the midst of which is a single cilium, and, in 
its active state, will take into its body crude material (that is, 
particles of indigo) if they be presented to it. The collar and ros- 
trum possess the power of polymorphism; and, when necessary, 
the whole body can be thus transformed. The latter is about 
soo inch in diameter in the calcareous sponges, and only half 
that size in those of the siliceous ones that I have examined ; and 
they are arranged in countless groups on the living sarcode of the 
areolar cavities of the sponge.” Of other familiar animaleules 
this resembles most the Difflugia, a kind of Amæba which throws 
out its pseudopodia from one particular part of its globular form; 
and if the zygosis among the Difflugie is a true conjugation, there 
is strong reason for believing any similar union of the sponge 
animalcules to be of the same nature. Though the author does 
not positively assert that the zygosis of the Difflugiz is a means 
of reproduction, he seems inclined to that belief, partly because 
that procedure is always confined within the limits of species ; 
and he seems to have traced a corresponding link in the history 
of the sponges. 
Finally, the author, having noticed a tendency to speak mor~ 
decidedly in microscopical inquiries than our powers seem to him 
to justify, condemns as unphilosophic the usage of those who call 
the parts of the lower organisms structureless. A wall or layer 
may be so dense and conspicuous as to be readily observed and 
named, yet it would be unphilosophic to call it wanting if only 
infinitely delicate and therefore imperceptible. The leg of Euplotes 
is “ probably” complicated in its muscular structure, and there 
are textures in the Spongiadæ, he doubts not, which are distant 
and misty hints of development, which in the higher animals are 
recognized by the coarsest sense. 
MULTIPLICATION or WHEEL ANIMALCULES BY BUDDING. ~ 3 
Greef has no difficulty in confirming the asexual reprođugtid" Q 
the Vorticellæ by fission, but reaches a very different conelorigi 
in regard to the formation of the budlike structures which he a 
are not buds at all, products of their bearer, but the products 
