I CAMERON 



VERTEBRATE STRIATED MUSCLE 87 



phenomena. For example, many of the nuclei would necessarily 

 become "pale and poor in chromatin" owing to their distension with 

 achromatic material (Figs. 2, 6 & 7). Again, the "vacuolations" are 

 capable of being interpreted as the pools of this freshly discharged 

 substance (Figs. 3 & 5), which later mingle with the sarcoplasm, and 

 would naturally cause it to appear "more homogeneous." It might be 

 further suggested that the "large clear vacuoles" described by Graham 

 Kerr^ in the myoblastic tissue of Lepidosiren embryos may possibly 

 be reservoirs of this nascent achromatic material. 



V. The "Achromatin Function" of the Nucleus. 



This discharge of achromatic material from the nuclei of develop- 

 ing muscle tissue confirms results which the author obtained many 

 years ago in the embryonic retina,^ in which it was shown that the 

 neuroblast-nuclei freely extruded an achrorhatic fluid substance. 

 I described this phenomenon as the "achromatin function" of these 

 nuclei. It is thus interesting to note that a similar function can be 

 shown to exist very definitely in muscle tissue as well. These observ- 

 ations are likewise confirmatory of riecent results obtained by Dr. 

 R. J. Gladstone and the writer^ from a study of the cell-elements of the 

 blastoderm, in which we showed that the nascent endoplasm immedi- 

 ately surrounding the nucleus is a derivative of nuclear metabolism. 

 This zone is remarkably achromatic in its reaction to staining agents,, 

 and thus bears a striking contrast to the remainder of the cytoplasm. 

 Thus on p. 226 we state that "protoplasm may be differentiated into 

 endoplasm and ectoplasm. The nascent endoplasm forms a clear 

 highly refractile zone immediately surrounding the nucleus. This 

 merges into a more mature endoplasm, which in its turn undergoes 

 transition into a granular ectoplasm. The nascent endoplasm, the 

 more mature endoplasm, and the ectoplasm represent three stages in 

 the genesis of protoplasm. It is a well recognised fact that the 

 protoplasm of every living tissue has a limited period of activity during 

 which its vitality is constantly being revived and rejuvenated by 

 regulated supplies of nascent material. The latter is apparently a 

 derivative of the nucleus and is discharged from this in the form of 

 nascent endoplasm. It would appear, therefore, that nutritive material 

 ingested by the cytoplasm receives its final elaboration in the nucleus. 

 From this standpoint we would argue further that the nascent endop- 

 lasm possesses the greatest activity, whilst the functions of the ectop- 



^op. cit. 



2Jour. of Anat. and Phys., Vol. XXXIX, 1905. 



30p. cit. 



