av THE MATURE OF CELL-ORGANIZATIOX. 85 



The meshes of the cytoplasm are filled with a fluid sub- 

 stance, commonly called the cytoplasmic fluid, or to use 

 Haeckel's term, the cytolymph. 



The cytoplasm is, however, the only living portion of the 

 cell-body, and hence properly belongs to the category of 

 protoplasm in the more strict technical sense of the term. The 

 cytolymph is the inert, passive, non-living portion of the 

 cell-body. Besides the cytolymph, there usually exist a number 

 of non-living bodies in the cell-body, as yolk-granules, oil drops, 

 debris of food, zymogen granules, etc., according to the nature 

 of different cells. These non-living substances altogether 

 belong to the group known as metaplasm or paraplasm, in 

 contradistinction to the substance which is the real living 

 element of the cell the protoplasm. 



The contents of the nucleus (caryosome) may be arranged 

 also into two .similar groups of living and non-living elements. 

 The chromosome is distinctly protoplasmic in character, and so 

 is the fine net-work of the " achromatic " thread-like substance 

 which is often found traversing the nuclear cavity. In several 

 cases, if not in all, these filaments are the actual continuation 

 of the cytoplasmic net-work existing around the nuclear 

 membrane. 



The fluid substance which bathes these semi-solid living 

 constituents of the nucleus is known as nuclear fluid or caryo- 

 lympJi. In the caryolymph there exists a body known as the 

 nnclcolits. In certain cases, the filaments of the chromosome 

 have been found passing through the substance of the nucleolus 

 or directly ending in it. Sometimes only one nucleolus exists 

 in each nucleus, while in other cases over .one hundred nucleoli 

 may be found in one nucleus. The number of nucleoli is quite 

 variable in different cells, but fairly constant in a given species 

 of cell. The nucleolus is not a permanent body in the nucleus. 

 It may exist at one stage of the cell, and may disappear at the 

 next. The micro-chemical reaction of the nucleolus is entirely 

 different from that of the chromosome. It appears probable 

 that three or more different bodies are included under the 

 same name of nucleolus. Indeed, one sees no reason why the 

 inside of the nuclear membrane may not be used as a deposi- 



