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Zoology. 439 
tion which divides it into two segments or distinct globules, and each of 
these segments seems to become a centre, which tends to envelope 
itself in a portion of the-surrounding granulations, separating them from 
cells which are entangled by its fellow. We should say, in short, that 
the vitelline sphere, excited simultaneously by two centres of action, 
yields to each of these centres half the substance of which it is com- 
posed, and thus divides into two segments which are immediately ren- 
dered spherical ; each segment of ‘the vitelline sphere, being furnished 
with the oleaginous globule which has excited the separation, then be- 
comes in its turn the seat of a similar process, and the division of its 
central globule induces that of the secondary sphere which contains it. 
This is the manner in which the phenomenon of the multiplication of 
the vitelline spheres ensues ; but this phenomenon, which we have 
considered as the result of a double influence simultaneously exerted 
upon each of the segments of the vitellus by the division of the fatty 
globe which occupies its centre,—this phenomenon, I say, seems to 
refer to a still deeper cause, and so to speak, to be nothing more than 
the external and consecutive repetition of a more intimate and previous- 
ly completed process. In fact, each central fatty globule contains in 
its interior a much smaller generating globule, and which appears, in 
regard to the fatty globule, to play the same part as the fatty globe ful- 
fils with regard to the vitelline spheres by which it is enveloped. So 
that if we review the whole of the facts which the vitellus presents 
during the transformations which we have described, we find that the 
elements to which these metamorphoses give rise are derived from one 
another in a continued series, and are all the result of a triple envelop- 
nt. 
This envelopment commences by the appearance of a primordial 
globule within the vitelline spheres; the globule then becomes a centre, 
around which the fatty globule is condensed ; the latter subsequently re- 
solves itself into two distinct fragments; and these fragments, enveloping 
themselves with the vitelline matter, produce the granular spheres, the 
mode of multiplication of which I have previously described. 
The formation of the organic spheres by successive envelopment 
around a centre, and their multiplication by subdivision, are such gen- 
eral facts as to require the whole attention of physiologists. They are 
observed in the vitellus of Mammalia, Batrachia, the osseous fishes, 
Mollusca, insects and worms. The so frequent production of these 
particular forms of matter proves, in opposition to the opinion of 
Schleiden and Schwann, that organized bodies are not exclusively com- 
posed of cells; but that other elements may also enter into the compo- 
sition of their tissues, and that the organic spheres ought to be reckoned 
among these elements. They do not in fact appear only as a transitory 
