226 CLARKE, ON STRIPED MUSCULAR FIBRE. 



fibrillation of the blastema between the densely crowded 

 nuclei, with which they become, as it were, encrusted 

 through a condensation of the surrounding blastema, which 

 also cements them together. Sometimes these masses assume 

 a cylindrical shape, although the elements which compose 

 them have but little regularity of arrangement (fig. 9). Much 

 more frequently, however, the fibres first formed, having 

 increased to a variable degree of thickness, become connected 

 together by the intervening substance, in which new fibres 

 are also developing, to form bodies or masses of different 

 shapes (fig. 9/). Sometimes a number of fine and more or 

 less wavy fibres are cemented side by side, and encrusted with 

 groups of nuclei, which carry on the process of fibrillation in 

 the intervening blastema, as at fig. 10 a and fig. 9 b ; or fibres 

 of different diameters wind their way through groups of nuclei, 

 which surround them like clusters of grapes, as at fig. 10 b. 

 In some instances they resemble the loosened or untwisted 

 fibres of a rope, entangling a number of nuclei (fig. 9 a and b) ; 

 while in others they are arranged in a kind of plexus of a 

 more or less uniform character, and supported by the inter- 

 vening and condensed blastema, in which new fibres are form- 

 ing (fig. 9 c). Occasionally, but not often, at this period of 

 development, I have found some of these fibres distinctly and 

 beautifully striated, as shown at fig 10 c. The large fusiform 

 bodies (fig. 9 e e') have often a striking resemblance to organic 

 muscular fibre-cells, but enclose a variable number of nuclei. 

 Some of them are comparatively short and broad, and contain 

 two or more nuclei, like those by which they are siu'rounded. 

 Similar appearances, however, are frequently assumed by 

 portions broken from a longer mass. Many of them are 

 apparently in different stages of transition into long, nucleated, 

 and nearly cylindrical fibres. In the course of this transition 

 their surfaces become plain and smooth, their nuclei multiply 

 by division, and are disposed in more regular series, with their 

 longer axes sometimes transverse. Frequently they are much 

 dilated in the middle, from which they contract into broad 

 but tapering fibres (fig. 9 e) . In many cases, however, the tran- 

 sition is more gradual, as at e ; while a great number have 

 assumed the form of large fibres of nearly uniform diameter, 

 and lie side by side in close apposition (A). As incubation 

 proceeds, these fibres increase both in number and develop- 

 ment, but at any one period until the thirteenth or fourteenth 

 day they assume a great variety of forms. On the twelfth 

 day many of them have still the appearance of long, fusiform 

 cells, which taper into long and comparatively narrow fibres 

 (fig. 11). Their dilatations, in general, according to their 



