84 THE ROYAL SOCIETY OF CANADA 



made by Macallumi j^ 1887, and by Eyclesheimer^ in 1904. It is 

 not intended to discuss here the mode of differentiation of the primitive 

 body segments and myotomes, more particularly as this subject has 

 been treated by Balfour,^ Kastner, * Kerr, ^KoUmann» and Maurer,^ 

 and in a very elaborate and exhaustive manner by Bardeen* and 

 Lewis^ in recent memoirs. 



The mesoblast from which striated muscle is developed (e.g. 

 a myotome) exhibits, during the earliest phases, the typical structure 

 of mesenchyme, namely, strands of protoplasm with nuclei irregularly 

 scattered throughout these. (Fig. 9). During the whole research 

 I have been unable to discover the existence of separate "muscle cells" 

 or myoblasts, even in the earliest stages. In fact the structure 

 exhibited by developing muscle tissue absolutely confirms the results 

 of a recent paper by Dr. R. J. Gladstone and the writer, i» in which we 

 showed that there was a structural continuity of the cell elements 

 during the early stages of development of the vertebrate embryo, 

 which was primary in character, that is to say, it had existed from the 

 very commencement of segmentation. Thus we found that division 

 of the nuclei was followed by an incomplete separation of the cyto- 

 plasm, the result being that the blastoderm persisted as one con- 

 tinuous protoplasmic mass or network with nuclei at the nodes. The 

 only suitable term we could invent to apply to this structural appear- 

 ance was Plasmodium. I find that this plasmodial or syncytial 

 condition persists very definitely in developing muscle, constituting 

 the myo-syncytium. Thus one of the first results of this investigation 

 was to controvert the old theory advanced by Schwann that a muscle 

 fibre was formed by the fusion of originally discrete cell elements. 

 It also disposes of the view expressed many years ago by Remak, 

 that each muscle cell is the direct derivative of a single myoblast. 

 On the other hand the results incorporated in this memoir support 

 the view of Godlewski, who has shown that in the rabbit embryo the 

 myoblastic tissue is essentially of the nature of a syncytium. It may 

 be mentioned that Caroline MacGilP^ has proved the same fact in 

 developing non-striated muscle, while M. Heidenhain^^ h^s shown 

 that the heart muscle in the duck embryo presents in the early stages 



iQuart. Jour. Micros. Sci., 1887. 



2Amer. Jour, of Anat., Vol. Ill, 1904. 



'Op. cit. 



*0p. cit. 



^Trans. Royal Soc. Edin., Vol. 41, Pt. 1., 1904. 



8, ">, 8 and «Op. cit. 



"Jour. Anat. and Phys. Vol. 50, 1916. 



"Internat. Monatschrift fur Anat. und Phys., Bd. XXIV, 1907. 



i^Anat. Anzeig. Bd. XX, 1902 and Ergeb der Anat. Bd. VIII, 1898. 



