96 THE ROYAL SOCIETY OF CANADA 



IX. Conclusions. 



1. A striated muscle fibre has no developmental relationship 

 whatever to a single "cell." 



2. The mesenchyme from which striated muscle is developed, 

 exhibits the structure of a syncytium- — the myo-syncytium as the 

 author would prefer to term it. 



3. There are two very distinct phases in Myo-genesis which have 

 not been previously described, namely, a nascent or achromatic and a 

 more mature or fibrillar phase. 



4. This comparatively achromatic material which undergoes 

 fibrillation is partly at least a derivative of the metabolic activity of 

 the nuclei of the myo-syncytium. 



5. In lower vertebrate typés the yolk granules that lie scattered 

 throughout the Myo-syncytium during the early stages of develop- 

 ment are attacked and digested by some neiv potent substance which 

 is suddenly discharged into the tissues. The writer has already demon- 

 strated in the case of embryonic nerve tissue that this is a nascent 

 achromatic material probably discharged from the nuclei, which 

 possesses the properties of an unformed ferment or enzyme. 



6. Concomitantly with the disappearance of these yolk granules 

 the cell-nuclei become enlarged and turgid, owing to the ingestion by 

 them of some of the constituents at least of the digested yolk. The 

 author has previously demonstrated in several communications 

 this ingestion on the part of neuroblast-nuclei. 



7. It would appear, then, that the final stages of ingestion and 

 storage of food material take place in the cell-nucleus. 



8. The nucleoli of the myo-syncytium become greatly enlarged 

 in Amphibian types, in which they appear to be of particular import- 

 ance as storehouses of chromatin. 



9. This store of nuclear chromatin becomes partially retrans- 

 formed into a fluid achromatic substance which at first distends the 

 nuclei to an enormous extent and finally becomes discharged as nascent 

 endoplasm, leaving some of the nuclei in a remarkably collapsed 

 condition. 



10. These alternating phases of turgidity and collapse of the 

 nuclei are constantly going on. 



11. The result of this discharge is to increase enormously the 

 amount of peri-nuclear material, which is thus for the most part 

 composed of an entirely neiv substance ready to undergo fibrillation 

 and form muscle fibrils. 



12. This nascent achromatic material soon "undergoes a mysteri- 

 ous process of maturation or "chromatisation" along very definite 

 lines of direction. 



