11 
structural adaptation in the Zoospore (animal or vegetable.) Cienkowski's 
observations prove that certain Monads take in food and pass through phases 
of development which entitle them to be considered animals. 
In their motile stages, the Monad body consists of a naked plasm, con- 
taining vacuole and nucleus. In the absence of all definite form, this body is 
the equivalent of an Amoeba ; but with the addition of a tail, which is often 
developed, it is a Zoospore, an organism equally mobile with the Amceba, 
but differing in the manner in which its mobility is exercised. In after 
periods of the Monad's life a motionless encysted condition obtains, during 
which assimilation of food previously taken in goes on, until a new generation 
of Zoospores begins in a sac contained within the capsule of the encysted 
parent. This encysted stage of the Monad yields in one species Amoeboid 
forms like actinophrys, in another a cluster of Zoospores, — the latter form 
of reproduction being in all respects the exact parallel of the encysted state 
of algae, &c. 
Again, certain infusoria exhibit an encysted state of two kinds— one 
corresponding with the motionless reproduction cyst of alg», the other with 
the monad cyst full of Zoospores, 
The motility of the pseudopodia of Rhizopods is obviously of the same kind 
as that of the Amaeboid substance. The pseudopodia look indeed more like 
"organs" of motion, but their temporary form and function implies no 
further structural adaptation than that of the Amoeboid mass. 
Facts such as these prove, in my opinion, that there is throughout the 
lower forms of animals an approach towards specialisation of functions, 
associated in each case with a correlative change of molecular constitution. 
If Amoeboid forms of matter be destitute of structure in the sense of distinct 
apparatus developed and set apart for the constant exercise of a particular 
function, such imperfect specialisation of function and incomplete differen- 
tiation of the organic matter by no means warrants the assumption, that 
this matter is intrinsically indifferent, and without any trace of organization. 
With respect to the place of the typical Amoeba in our classifications it 
follows, 1 think, from the views here expressed, that this animal must find 
its position in the scale according to its whole life history. The possession 
of a body composed of contractile plasm is, as we know, a common character 
of all Protozoa at some period of life, — probably also a common character of 
all living creatures in their elementary state. The Amoeboid state of a white 
blood corpuscle, even in man himself, is to all appearance the same as that of 
the body of Protogenes, and this fact is well expressed by Huxley in his recently 
published Lecture on the Physical Basis of Life. To determine the proper 
limits of the Amoeba as a species, the complete revelation of its life-history 
