MORPHOLOGY 37 



phore-bearing Protozoa are variously colored, and those with 

 symbiotic algae or cryptomonads are also greenish or brownish 

 in color. Furthermore, pigment or crystals which are produced 

 in the body, may give protozoans various colorations. In several 

 forms pigments are diffused throughout the cytoplasm. For ex- 

 ample, many dinoflagellates are beautifully colored which, ac- 

 cording to Kofoid and Swezy, is due to a thorough diffusion of 

 pigment in the cytoplasm. Stentor coeruleus is ordinarily blue- 

 colored, the pigment responsible for which was called Stentorin 

 (Lankester) and is lodged in granules between the surface striae; 

 and rose- or purple-coloration of several species of Blepharisma 

 appears to be due to a special pigment, zoopurpurin (Arci- 

 chovskij) which is lodged in the ectoplasmic granules often called 

 protrichocysts (p. 65). The development of zoopurpurin is 

 definitely correlated with the sun-light, as shown by Giese. 

 Deeply pink specimens will lose color completely in a few hours 

 when exposed to strong sun-light and the recoloration takes 

 place in darkness very slowly. 



The extent and nature of the cytosomic differentiation differs 

 greatly among various groups. In the majority of Protozoa, the 

 cytoplasm is differentiated into the ectoplasm and the endo- 

 plasm. The ectoplasm is the cortical zone which is hyaline and 

 homogeneous. In the Ciliophora, it is a permanent and distinct 

 part of the body and contains several organellae; in the Sarcodina 

 and the Sporozoa, it is more or less a temporarily differentiated 

 zone and hence varies greatly at different times and, in the 

 Mastigophora, it seems to be more or less permanent. The endo- 

 plasm is more voluminous and fluid. It is granulated or alveo- 

 lated and contains various organellae. While the alveolated 

 cytoplasm is normal in forms such as the members of Heliozoa 

 and Radiolaria, in other cases the alveolation of normally gran- 

 ulated or vacuolated cytoplasm indicates invariably the degen- 

 eration of the protozoan body. 



In numerous Sarcodina and certain Mastigophora, the body 

 surface is naked and not protected by any form-giving organella. 

 According to observations by Kite, Howland, and others, the 

 surface layer is not only elastic, but solid, and therefore the name 

 plasma-membrane may be applied to it. Such forms are capable 

 of undergoing amoeboid movement by formation of pseudopodia 

 and by continuous change of form due to the movement of the 



