THE FUNDAMENTAL ORGANIZATION 49 



the derived organization. Some substances are found in all Protozoa 

 and these may be considered the raw materials from which the 

 derived organization is manufactured. 



Although they are intimately related, it is convenient to describe 

 the constituents of the nucleus and those of the cytoplasm under 

 separate headings. 



I. NUCLEAR SUBSTANCES AND STRUCTURES OF THE 

 FUNDAMENTAL ORGANIZATION. 



The term "nucleus" is ordinarily applied in a morphological rather 

 than a physiological sense. If the activities of the component parts 

 of the nucleus are absolutely necessary for the maintenance of life 

 of the cell, then, in some cases such as Holosticha, Trachelocerca, 

 or Vile phis, such activities must be performed by substances which 

 appear to be identical with chromatin but which are distrib- 

 uted throughout the cell. On the other hand, it is highly probable 

 that some functions are possible by virtue of the physical prop- 

 erties of a definite, but permeable, nuclear membrane, as in the 

 tissue cells of Metazoa. It is this type of membrane-bound nucleus 

 that we find in the vast majority of Protozoa. 



Certain constantly recurring substances are characteristic of 

 protozoan as of metazoan nuclei, but some types of arrangement 

 and combination of these substances are typical of Protozoa and 

 are rarely found in Metazoa. The most universal of these nuclear 

 constituents are (1) chromatin, which is sometimes called nuclein 

 or identified as such; (2) nuclear sap or nuclear enchylema filling 

 the spaces of the linin reticulum; (3) nuclear membrane which 

 forms a permeable partition between cytoplasm and nucleoplasm; 

 (4) plastin, often so called without being specifically identified as 

 such; also termed paranuclein, or pyrenin. Plastin by itself forms 

 true nucleoli which are comparatively rare in Protozoa. In addition 

 to these, kinetic elements are characteristic of the majority of 

 protozoan nuclei, and these in the present work will be called 

 endobasal bodies. 



It must be frankly admitted that very little is known in regard 

 to the chemical nature of these various constituents of the nuclei 

 in Protozoa and much confusion exists in the literature owing to 

 the promiscuous use of these terms in relation to structural elements 

 of the nucleus without knowledge of the actual chemical make up. 



In their resting stages the nuclei of Protozoa present a bewildering 

 variety of forms and structures, differing in this respect from the 

 much less variable tissue nuclei of the Metazoa. Because of these 

 manifold differences students of the Protozoa have experienced great 

 difficulty in grouping nuclei for purposes of description. They 

 agree, however, in recognizing two primary nuclear types, the 

 4 



