468 EMBRYOLOGY OF THE TURTLE. Part III. 
appearance produced is as if the latter originated round the former, instead of 
the reverse, which is the natural process, as we have lately demonstrated; and 
this, no doubt, has given rise to the prevailing view of their genetic relation. 
This appearance may, however, very readily be accounted for, with the object in 
sight; but to put the picture before another's eyes in the mien of words, intro- 
duces an element in the demonstration always difficult to overcome, and most 
tryingly unprecedented in the present instance, not only from the intrinsic noy- 
elty of the subject, but also because a totally different imterpretation of the cell 
genesis, in other bodies, has swayed the minds of nearly all previous investigators. 
Hence we must bee an unwonted indulgence wherever, m our descriptions, there 
appear an unusual redundancy of words, and repetitions of the same idea under 
different guises. 
If there had ever been found a free cell which in the least resembled the 
mesoblasts already developed in other cells, then the office of originating around 
itself a certain more transparent spherical substance, such as we call ectoblast, 
might possibly have been attributed to it. But in no instance has such a cell 
been discovered, nor any one at all approximating its feature; on the contrary, 
as we have already shown, all homogeneous cells which appear after the irregular 
granular state of the yolk are endowed with the physiognomy of  ectoblasts. 
The nearest approximation to such a mode of cell formation is exhibited in 
those instances where the mesoblast nearly fills the ectoblast; but this occurs 
not in the minutest cells only, (Pl. 9, fig. 8a, K, F,) it is equally seen at all 
stages of yolk cell growth, (Pl. 9, fig. 8a, A, B, C, D, fig. 6b, fig. 11d, a, and fig. 
lle,) even in the largest egys. Always, wherever a so-called nucleus is found, 
there is present a clear enveloping substance of lesser or greater thickness. — It 
would, therefore, be just as reasonable to argue that the largest cells origmated 
full-grown around this nucleus, which nearly fills them, as it would be to assert that 
this obtains in the minutest cells which present such features, excepting perhaps 
for the fact that these last are nearer related to the dimensions at which the like 
are generated; for, in truth, as far as argument from appearances is concerned, 
there is no difference, except in size; and it requires but a moment to magnify 
the smaller to such an amount that they will appear identical im every respect 
with those actually far exceeding them in bulk (PI. 9, fig. 8a, K and C, or fig. 
7d). How easily may we, on the contrary, trace the converse mode of genesis! 
How naturally can one follow the steps of the various stages, from a simple, 
clear cell, at first condensing a portion of its contents into a cloudy mass, till 
the cloud grows more and more defined in outline and globular in’ shape, and 
at last displays itself as a perfect sphere, which finally proceeds to grow, till, by 
the time the ege has a shell, it absolutely fills the ectoblast (Pl. 9a, fig. 33b, 
