38 GENERAL SKETCH OE THE CELL 



lum undoubtedly represent aggregations of such granules, but whether 

 the latter completely fuse or remain always distinct is unknown. 

 Even the chromosomes at certain stages appear perfectly homoge- 

 neous, and the same is sometimes true of the entire nucleus, as in the 

 spermatozoon. It is nevertheless possible that the chromatin-gran- 

 ules have a persistent identity and are to be regarded as morpho- 

 logical units of which the chromatin is built up.^ 



Heidenhain ('93, 94), whose views have been accepted by Rcinke, 

 Waldeyer, and others, has shown that the "achromatic" nuclear net- 

 work is likewise composed of granules, which he distinguishes as 

 /tint/ianiu- or <u;jr//;v;;/^?//;/-granules from the has ic/iroiULi t i fi-gr3.\\\i\Q.s> 

 of the chromatic network. Like the latter, the oxychromatin-granules 

 are suspended in a non-staining clear substance, for which he reserves 

 the term //;////. Both forms of granules occur in the chromatic 

 network, while the achromatic network contains only oxychromatin. 

 Thev are sharply differentiated by dyes, the basichromatin being 

 coloured by the basic tar-colours (methyl-green, saffranin, etc.) and 

 other true "nuclear stains"; while the oxychromatin-granules, like 

 many cytoplasmic structures, and like the substance of true nucleoli 

 (pyrenin), are coloured by acid tar-colours (rubin, eosin, etc.) and 

 other "plasma stains." This distinction, as will appear in Chapter 

 VI I., is possibly one of great physiological significance. 



Still other forms of granules have been distinguished in the nucleus 

 by Reinke ('94) and Schloter ('94). Of these the most important 

 are the " oedematin-granules," which according to the first of these 

 authors form the principal mass of the ground-substance or " nuclear 

 sap " of Hertwig and other authors. These granules are identified 

 by both observers with the " cyanophilous granules," which Altmann 

 regarded as the essential elements of the nucleus. It is at present 

 impossible to give a consistent interpretation of the morphological 

 value and physiological relations of these various forms of granules. 

 The most that can be said is that the basichromatin-granules are 

 probably normal structures ; that they play a principal role in the 

 life of the nucleus ; that the oxychromatin-granules are nearly related 

 to them ; and that not improbably the one form may be transformed 

 into the other in the manner suggested in Chapter VII. 



The nuclear membrane is not yet thoroughly understood, and 

 much discussion has been devoted to the question of its origin and 

 structure. The most probable view is that long since advocated by 

 Klein i^yd)) and Van Beneden ('83) that the membrane arises as a 

 condensation of the general protoplasmic substance, and is part of 

 the same structure as the linin-network and the cytoplasmic mesh- 

 w^ork. Like these, it is in some cases "achromatic," but in other cases 



1 Cf. Chapter VI. 



