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the plasson as the primitive condition. But in the plasson 
the nucleolus appears before the nuclear layer. If we identify 
plasson with the blastema, such as Schwann understood it, 
we shall return to the views of the celebrated histologist who 
assigned to the cell a centrifugal evolution. The parts then 
develop from within outwards, and the nucleolus assumes as 
great an importance as, or one comparable to that of, the 
nucleus. It is not easy to reconcile this with the fact of the 
possible disappearance of this element of the cell, as observed 
by me in the Gregarina. 
Haeckel has, with much reason, arranged the Gregarine 
by the side of the Amcebe in his group of the Protoplasta ; 
he considers the Gregarine as parasitic Amebe. ‘1 regard 
the Gregarine as Ameebe, which have become degenerate 
(ruckgebildet) by parasitism.” Every parasitic animal is 
evidently derived from a form originally living in the state 
of liberty. It is clear that the Gregarine are at least as 
intimately related to the Amcebe as are the Lernzans to the 
free Copepods. But whilst one observes generally in para- 
sitic animals a retrogressive development, the Gregarine, 
instead of retrograding, appear to me to be raised in the 
scale by their parasitic life. Evidently the Gregarine are 
very high “ Lepocellule,” as the study of their entire organi- 
zation proves. 
By elaborate researches on the chemical composition of 
protoplasm (analysis of the protoplasm of the Myxomycete), 
Kihne has demonstrated the complex nature of this material. 
Protoplasm is formed of a mixture of different albuminoid 
matters, among which are especially found myosin, lecithin, 
&c. Protoplasm contains, moreover, a substance very similar 
to vegetable cellulose.t In accordance with this, it is very 
evident that the progressive differentiation of cells and their 
characterisation from the physiological point of view, depends 
on the preponderating accumulation of one or other of these 
principles, and on the separation of this or that from the 
other elements of the protoplasm (law of localisation). 
The muscular cell contains a larger quantity of myosin, 
able to separate itself progressively from the other elements 
of the protoplasm in proportion as it is formed. We know 
that in a monocellular being, somewhat elevated in organi- 
sation, this myosin tends to separate itself also, and to become 
deposited, in one form or other, under the cuticular layer, and 
to bring into existence in this way, in the cell, a locomotive 
system, comparable, in a physiological sense, to that of the 
nematoid worms. The cuticle in the Nematoids is a sort of 
1 Verbal communication from Professor Kuhne. 
