THE INFUSORIA 



189 



ously distributed. The vesicular structure, in which the nuclear 

 substance is so distributed as to leave more or less space filled with 

 "nuclear sap," is almost never seen, the macronucleus appearing 

 solid and completely filled with chromatin. Biitschli described the 

 finer structure as almost invariably alveolar, the meshes correspond- 

 ing to those of the surrounding plasm. The entire network stains 

 deeply with the nuclear dyes, but at certain stages, especially 

 during division, distinct fine lines can be made out connecting the 



D 



JVL 



F 



Fig. 103. Types of macronuclei. [SAVILLE KENT.] 



A. Macro- and micronucleus of Loxodes rostrum O. F. M. B. Of Nyctotherus cordiformis 

 Leidy. C. Macronucleus of Plagiotoma lumbrici Duj. D. Dendrosoma radians S. K., a young 

 nucleus. E. Dendrosoma radians S. K. F. Stentor polymorphus Ehr. G. Stylonychia mytilus 

 O. F. M. H. The same in division. N, the macronucleus ; n, the micronucleus. 



chromatin granules, and corresponding to the linin reticulum of 

 most nuclei. In some cases (e.g. Loxophylhim} a permanent 

 spireme is present, as in the nucleus of cells frdm the salivary gland 

 of Chironomus larvae, and is transversely striated, indicating disks 

 which Balbiani ('90) thought are alternately chromatin and linin 

 (Fig. 104). In many cases there are internal modifications of the 

 nuclear material forming so-called "nucleoli," although there is a 

 possibility that these structures are similar to the intranuclear bodies 

 found in Mastigophora. 



In many macronuclei a peculiar division of the organ is made by a 



