8 CLARKE, ON STRIPED MUSCULAR FIBRE. 
ultimately inclosed by the striated substance to which they 
give origin. 
With respect to the first of these statements, the question 
to be decided is, whether these formative bodies are to be 
regarded as true nucleated cel/s. In the regenerate tissue of 
the tadpole, according to Deiters, they are real cells, possess- 
ing distinct envelopes. Now, although in this particular 
case | am not prepared to offer any opinion from direct 
observation, since the season had already passed for making 
the necessary examination before the publication of the 
Deiters’ paper, yet I think I may safely assert that in 
man, mammalia, and birds, the granular substance surround- 
ing the nuclei, and concerned in the development of the 
muscular fibres, have no envelope or cell-wall in the proper 
sense of the word, and that these bodies are not entitled to 
be considered as nucleated cells.* It is true, as I have already 
shown, that the granular substance sometimes assumes the 
form of a fusiform cell; but, if the process of development 
be examined in very young embryos, the tapering or conical 
prolongations of the nucleus may be observed in different 
stages of formation, and to consist frequently, at first, of 
delicate streaks of the finely granular blastema. But it 
very commonly happens, as I have also shown, that the 
intervening blastema cements the nuclei together, without 
forming a separate mass around each. In other instances, as 
represented at e, fig. 11, in the chick, and at m, fig. 14 (Pl. XI), 
in the pig, a fibre originates in the blastema, between series 
of nuclei, at some distance asunder, which are each con- 
nected with the fibre by a more or less globular, oval, or 
fusiform mass. Fig. 14, like the others, is an exact repre- 
sentation of a fibre from the dorsal muscles of a feetal pig of 
not quite an inch in length. The granular blastema on the 
left border of the middle nucleus had not yet actually 
assumed the appearance of a fibre. The free edges of these 
delicate and variously shaped masses of blastema are at first 
frequently uneven, ragged, or, at least, not sharply defined, 
and contrast strongly with the very distinct and well-defined 
wall of the nucleus itself. But when a fine fibre or lateral 
band has formed along each side of one of the masses 
surrounding the nucleus, and has joined its fellow at both 
ends (as at the lower part of m, fig. 14; the upper part 
of e, fig. 11, and elsewhere), this investing substance has 
* Tt is necessary to state that an abstract of my present communication 
was received by the Royal Society of London, on November 21, 1861; read 
January 16, 1862; and published in No. 48, vol. xi, of the ‘ Proceedings of 
the Royal Society.’ 
