358 On the Contractile Substance of the Polythalamia. 
cular fibre, as also a comparative anatomical consideration of 
the entire structure of the Polythalamia and the animal organ- 
‘sms in which distinct muscular fibres occur. By the words, 
“that the contractile cortical layer of the Polythalamia is an 
undeveloped muscular mass, sarcode, or protoplasm,” is as little 
or even less advance made than by the expression “ that the 
Polythalamia are undeveloped vertebrata.” 
In regard to the motory phenomena, in which the contractile 
action is expressed, the differences are very striking at first sight. 
In the case of the muscular fibre (for the sake of simplifying the 
comparison and, by comprising the extremes, allowing the law 
to be surveyed with great nicety), a cylindrical contractile sub- 
stance becomes converted by contractile power into a disk with 
a circular outline, possessing nearly or absolutely the same 
volume; in the case of the contractile cortical substance of the 
Polythalamia, a disk with a circular outline into a cylinder. Accu- 
rate examination, however, teaches us that different forms only are 
concerned, under which the contractile substance is apphed and 
its contractility realized for the accomplishment of spontaneous 
and involuntary movements and functions in the organism. As 
regards the expression of the contractile action, 2. e. of the 
movement of the contractile particles in a certain direction cor- 
responding to each change of form of the contractile structure, 
the distinction of a so-called active or passive state is of secon- 
dary importance. The former force, which urges and transfers 
the contractile particles from a position arranged according to 
the long axis of a cylinder, into that in which the contractile 
particles are situated with regard to the axis of the cylindrical 
section and in the form of a disk, is in every respect exactly 
the same, by whatever cause, on transition imto the state 
of rest, the displacement of the contractile particles from the 
discoidal form into that of the cylinder is produced; and so 
vice versd in regard to the contractile action occurring in the 
Polythalamia. 
If, however, the transition of the contractile structure into 
the so-called state of rest and the form of this state is also 
taken into account as an active motory phenomenon, the muscular 
fibre and the contractile cortical layer of the Polythalamia agree 
perfectly as regards their contractile action. In both are recog- 
nizable the same fundamental forms, which appear in the alter- 
nation of two contractile tissues in a state of action, viz. the 
elongated cylindrical, and the disk or plate, expanded in 
breadth or into the section of a cylinder—the difference referring 
simply to the circumstance that in the two contractile tissues, 
as already stated, quite independently of other morphological 
relations, the same fundamental forms are not conceived in the 
