CLARKE, ON STRIPED MUSCULAR FIBRE. 227 



lengtli, contain a variable number of nuclei, disposed in 

 regular series, with their longer axes often in a transverse 

 direction. In a few instances, however, as at fig. 11 a, I 

 found only a single and remarkably large" nucleus, which 

 occupied the entire breadth of the dilatation, and contained a 

 well-defined, granular nucleolus, of a correspondingly large 

 size. Sometimes the dilatations were seen to be repeated 

 twice or even thrice in the course of the same fibre, which, at 

 variable intervals between them, contained nuclei of an oval 

 form and of a breadth equal to themselves. 



But besides these fibres of later formation there was also a 

 considerable admixture of the kind first described. Many of 

 the latter were slender and delicate, with round and oval nuclei 

 as broad as the fibres themselves, and sometimes raised from 

 their surface (fig. 11 b). Others were thicker, with sharply 

 defined borders, and enclosed a granular axis, with round or 

 oval nuclei, which in some places were disposed in straight, 

 longitudinal series, but collected in others into small groups 

 (fig. 11 c c). Here and there they were found in the earliest 

 state of development, as represented at d. At e a succession 

 of round nuclei, in contact with the side of a slightly undulat- 

 ing fibre, were each enveloped in a delicate and nearly fusi- 

 form mass of condensed blastema, which converted them into 

 what had somewhat the appearance of nucleated cells. 



At this period of incubation both transverse and longitudi- 

 nal strise exist in some of the fibres, but are entirely absent in 

 others. The longitudinal are the first to make their appear- 

 ance on the surface, and in the form of simple or plain fibrillse, 

 which subsequently break up into series of dots or granules. 

 These granules are much coarser in some fibres than in others. 

 When they are small, on the same level transversely, and in 

 close proximity, they present, under a moderate power, the 

 appearance of transverse lines, which, however, by the use of 

 higher powers, may be resolved into separate granules that 

 belong to the longitudinal fibrillse. So long as the fibrillse 

 remain undivided or plain, the striations, therefore, are only 

 longitudinal. When the fibres are fusiform, these appearances 

 are most conspicuous, or perhaps visible, only in the coui'se 

 of the dilatations (see fig. 11 f, g). 



On the thirteenth or fourteenth day of incubation * some 

 of the fibres are more or less in the condition of those which 

 first made their appearance, but by far the greater number 



* At any given period of incubation there is generally, as the result of 

 accidental circumstances, some little difference in the degree of development 

 in eggs hatched under different hens. This I found to be the case with 

 regard to the three hens employed for the jjurposes of this inquiry. 



