THE NUCLEUS 



relatively passive bodies that represent accumulations of reserve- 

 substance or by-products, and play no direct part in the nuclear 

 activity (p. 93). 



it. The ground-substance, nuclear sap, or karyolymph, a clear sub- 



Fig. ii. Special forms of nuclei. 



A. Permanent spireme-nucleus, salivary gland of Chironotnus larva. Chromatin in a single 

 thread, composed of chromatin-discs (chromomeres), terminating at each end in a true nucleolus 

 or plasmosome. [BALBIANI.] 



B. Permanent spirerne-nuclei, intestinal epithelium of dipterous larva Ptychoptera. [VAN 

 GEHUCHTEN.] C. The same, side view. 



D. Polymorphic ring-nucleus, giant-cell of bone-marrow of the rabbit ; c, a group of centro- 

 somes or centrioles. [HEIDKNHAIN.] 



li.. Branching nucleus, spinning-gland of butterfly larva (Pieris}. [KORSCHELT.] 



stance occupying the interspaces of the network and left unstained 

 by many dyes which colour the chromatin intensely. Until recently 



former are especially coloured by alkaline carmine solutions, the latter by acid solutions. 

 Still later studies by Zacharias, and especially by Heidenhain, show that the medullary 

 substance (pyrenin) of true nuclei is coloured by acid anilines and other plasma stains, 

 while the chromatin has a special affinity for basic anilines. Cf. p. 242. 



