THE PROTOZOA 



carried food-products in various stages of digestion and assimilation, 

 as well as excretory products in the form of granules similar in all 

 respects to those found in other Protozoa. Engelmann ('83) found 

 that in one of the Vorticellidae ( Vorticella campanula) the animal is 

 colored by diffuse green pigment, which he took to be chlorophyl, 

 and he further showed that oxygen is generated and that the animal 

 can assimilate like a plant, but that it is not limited to this kind of 

 nutrition, since it also takes in solid food through the mouth. Other 

 colored particles which are found in various kinds of Ciliata, espe- 

 cially in those forms which subsist upon plant food, are presumably 

 due to the coloring matter contained in the food. Schewiakoff ('89) has 

 shown that the colored balls which appear in some cases are merely 

 fluid drops colored with the pigment contained in Oscillaria and other 

 vegetable cells. In many cases, also, green algal cells live as sym- 

 bionts within the endoplasm. Le Dantec ('92) found that these cells 

 (Zoochlorelld) are apparently taken in as food and become inclosed 

 within gastric vacuoles, the fluids of which have no effect upon them. 

 Soon the vacuoles disappear and the algae are left free in the plasm, 

 where they live and multiply. There are also various fats and 

 excretory products either crystalline or granular in form. The 

 crystals, according to Schewiakoff ('93), are granules of calcium 

 phosphate. 1 Among the pigmented inclusions of the cell must be 

 noted the so-called "eye-spots " or stigmata, which, in some instances, 

 are accompanied by lenticular differentiations of various kinds. These 

 pigmented spots are, as a rule, mere heaps of granules colored either 

 red, brown, black, or orange, and are probably the same in function 

 as the similar products in Mastigophora. 



The protoplasm becomes more dense toward the periphery, and, 

 as in the Sarcodina, it finally becomes too compact for the granules 

 to penetrate. This outer portion is, therefore, comparable to the 

 ectoplasm of the less differentiated Protozoa. The importance of 

 this layer is seen in the fact that nearly all of the organs which 

 characterize the Ciliata, including the myonemes, cilia, membranes 

 and membranelles, the trichocysts, nematocysts, and the complex 

 membranes and tests, are modifications of, or are produced by, the 

 ectoplasm. In some forms the thickened plasm immediately adjoin- 

 ing the endoplasm is distinctly marked off from the more external 

 portions, forming a continuous layer around the entire body. This 

 layer, which is in reality neither ectoplasm nor endoplasm, but inter- 

 mediate between the two, is called the cortical plasm (Rindenparen- 

 chyma, Stein), and is characterized by the reduced size and number of 

 its vacuoles, by the absence of granules and streaming motion, and 



1 Cf. p. 286, infra. 



