78 PROTOZOOLOGY 



vacuole is a space in the cytoplasm, containing the fluid medium 

 which surrounds the protozoans and in which are suspended the 

 food matter, such as various Protophyta, other Protozoa or small 

 Metazoa. In the Sarcodina, the Mastigophora and the Suctoria, 

 which do not possess a cytostome, the food vacuoles assume the 

 shape of the food materials and, when these particles are large, it is 

 difficult to make out the thin film of water which surrounds them. 

 When minute food particles are taken through a cytostome, as is 

 the case with the majority of euciliates, the food vacuoles are usually 

 spherical and of approximately the same size within a single proto- 

 zoan. In the saprozoic Protozoa, which absorb fluid substances 

 through the body surface, food vacuoles containing solid food, of 

 course, do not occur. 



The chromatophore and associated organellae 



In the Phytomastigina and certain other forms which are green- 

 colored, one to many chromatophore s (Fig. 31) or chloroplasts con- 

 taining chlorophyll occur in the cytosome. The chromatophores vary 

 in form among different species; namely, discoidal, ovoid, band- 

 form, rod-hke, cup-like, fusiform, network or irregularly diffused. 

 The color of the chromatophore depends upon the amount and kinds 

 of pigment which envelops the underlying chlorophyll substance. 

 Thus the chromatophores of Chrysomonadina are brown or orange, 

 as they contain one or more accessory pigments, including phyco- 

 chrysin, and those of Cryptomonadina are of various types of brown 

 with very diverse pigmentation. In Chloromonadina, the chromato- 

 phores are bright green, containing an excess of xanthophyfl. In 

 dinoflagellates, they are dark yellow or brown, because of the pres- 

 ence of pigments: carotin, phylloxanthin, and peridinin (Kylin), the 

 last of which is said to give the brown coloration. A few species of 

 Gymnodinium contain blue-green chromatophores for which phyco- 

 cj^anin is held to be responsible. The chromatophores of Phytomon- 

 adina and Euglenoidina are free from any pigmentation, and there- 

 fore green. Aside from various pigments associated with the chro- 

 matophores, there are carotinoid pigments which occur often outside 

 the chromatophores, and are collectively known as haematochrome. 

 The haematochrome occurs in Haematococcus pluvialis, Euglena 

 sanguinea, E. rubra, Chlamydomonas, etc. In Haematococcus, it in- 

 creases in volume and in intensity when there is a deficiency in phos- 

 phorus and especially in nitrogen; and when nitrogen and phos- 

 phorus are present sufficiently in the culture medium, the haemato- 

 chrome loses its color completely (Reichenow; Pringsheim). Steinecke 



