88 THE ROYAL SOCIETY OF CANADA 



lasm are more of a passive nature, and are mainly in the direction of 

 maintaining structural continuity between neighbouring cell-elements." 



Many years ago I showed that in the embryonic retina^ this 

 achromatic nascent endoplasm has a powerful digestive action on the 

 yolk granules and even on the pigment granules of the retinal pigment 

 cells. Thus on p. 485 it is stated "A double proof of the fact that the 

 nuclear achromatin, of embryonic nuclei at least, possesses digestive 

 properties in the nascent condition, is furnished by its action on the 

 yolk granules and on the pigment granules of the retinal pigment 

 cells. This observation appears to lead one to the conclusion that 

 this nascent nuclear achromatin must contain an informed ferment or 

 enzyme — a statement which gathers interest in view of some recent 

 researches (especially by Hartog) on the existence of enzymes in 

 embryonic tissues. It has been further shown that many of the 

 nuclei absorb the digested yolk globule, and after elaborating it, 

 store it up as nuclear chromatin. It would thus appear that the 

 achromatin is that part of the nuclear organ which exercises the 

 digestive and ingestive action on food material, while the chromatin 

 is to be regarded as the primary product of nuclear metabolism. The 

 nuclear chromatin, again appears to be capable of retransformation 

 into a substance which in the nascent condition is achromatic in 

 character and is in this form extruded from the nucleus." 



It may be at once remarked that amphibian embryonic muscle 

 tissue in the earliest phases of its development confirms the results 

 of these cytological researches on the Amphibian retina. A study of 

 Figs. 8 and 9 which are from 19th and 20th day frog embryos res- 

 pectively, will serve to make this point clearer. These have been 

 photographed from sections of Amphibian mesenchyme which is in 

 process of transformation into striated muscle. Frog embryos were 

 chosen for the purpose of investigating this question, because the 

 tissues of this vertebrate type are loaded with yolk granules in the 

 early stages. Fig. 9, which is from an embryo only 24 hours older 

 than that represented by Fig. 8, shows here and there the earliest 

 phases of fibrillation in the form of minute dots placed in regulated 

 order (at points a, b, c, d.) The most striking point of contrast 

 between Figs. 8 and 9 is, however, the rapid disappearance of the 

 yolk granules which, it will be observed in Fig. 8, stain intensely with 

 iron-alum-haematoxylin, whereas in Fig. 9, they appear to have 

 nearly all vanished. As shown at points a and b in Fig. 8, and e and g 

 in Fig. 9, these granules become suddenly achromatic in their behav- 

 iour towards staining agents just as in the case of the embryonic 



lOp. cit. 



