INTRODUCTION 51 



fixed products of cell activity collectively known as metaplasmic 

 granules or metaplastids. All of these are formed during the vital 

 activities of metabolism some of them as reser\e stores of food 

 substance formed as products of the building up or anabolic processes 

 of metabolism, others by the destructive or catabolic processes. In 

 the former group are included many kinds of carbohydrate? such as 

 amylum (starch) ; paramylum (similar in composition to starch but 

 fails to give the characteristic blue reaction with iodine), karotin, 

 leucosin and cellulose, all of which are characteristic of chlorophyll- 

 bearing Protozoa although not confined exclusively to them; other 

 products of constructive metabolism which are more widely dis- 

 tributed, are fats, glycogen, paraglycogen, oils, albumin spheres, 

 etc. In the latter group, as products of destructive metabolism, 

 are included a great \-ariety of cr\'stals, pigment granules, chitin 

 and pseudo-chitin, and other more or less widely distributed pro- 

 ducts. These products of destructive metabolic activities are 

 frequently so abundant as to give the protoplasm a densely granular 

 appearance. 



The form and appearance of these various products of proto- 

 plasmic activities vary within wide limits and will be discussed more 

 fully in connection with the different classes of Protozoa. Many 

 of them serve a useful purpose as reserves in nutrition and other 

 physiological processes, while a niunber of them are used for pur- 

 poses of support, protection, or shell and skeleton building. Car- 

 bohydrate compounds, rarely in the form of starch, but abundantly 

 in the form of paramylum, are mainly confined to the chlorophyll- 

 bearing Protozoa where, in forms like Euglena they are the first 

 recognizable products of assimilation. After their formation they 

 may remain as a reserve store of nutriment. True starch occurs 

 in the Cryptomonadidse, Phytomonadidse, and in the Dinoflagel- 

 lata, while paramylum may occur, not only in the chlorophyll-bear- 

 ing types, but in many colorless forms as well {e. g. ChUomonas 

 jxiramecium, Astasia, Peranema, etc.). Glycogen-like bodies are 

 found in a few types of flagellates; true glycogen occurring in the 

 protoplasm of Pelomyxa palustris according to Stol(;' (1900), and in 

 the ciliates Paramecium, Opalina, (ilavcoma and Vorticella accord- 

 ing to Barfurth. Paraglycogen, also called zooamyliun, which 

 differs from glycogen in its solubility and in its color reactions 

 when subjected to sulphuric acid and iodine, is present in many 

 ciliates and flagellates as well as in some gregarines. Leucosin is 

 a carbohydrate in the form of highly retractile globules or balls 

 particularly characteristic of the Chrysoflagellidse and some of the 

 simpler ]\lonadida?. 



Oils and fats are widely distributed. Great oil globules are par- 

 ticularly characteristics of the Radiolaria where, in addition to 

 serving a useful purpose as reserves of nutriment, they also serve 



