THE MASTIGOPHORA 161 



from the perisarc as a naked cell. The protoplast is never com- 

 pletely adherent to its perisarc, but is capable of more or less 

 independent movement within it, and recedes from it upon the 

 formation of the resting-stage, and also in consequence of plasmo- 

 lysis. Its chemical composition is based upon a gelatinous substance 

 of carbohydrate nature, and in Dinobryon Klebs has found that the 

 perisarc gives the typical cellulose reaction. 



The periplast is always present in Lissoflagellates, but the 

 perisarc is a secondary formation secreted by the protoplast through 

 the periplast, and may or may not be present. 



The perisarc may occur as a capsule closely investing the cell 

 with an apical opening for the flagellum, as in Chrysococcus and 

 Trachelomonas. In the Chrysomonadine genera Synura, Mallomonas, 

 Hymenomonas, and Microglena the protoplast is closely adherent to 

 the perisarc, which here tends in the direction of a true cell-wall 

 and is called a cuticle. In Hymenomonas by exception the perisarc 

 divides with the cell. 



The most familiar form in which the perisarc is developed is 

 that of a cupule, as in the calyptoblastic Hydroids. Well-known 

 examples of cupule-formation are presented by the genera Bicosoeca, 

 Poteriodendron, Salpingoeca (Fig. 7 (6, 7)), Dinobryon, etc. Some genera 

 secrete a stalk only, Avithout a cupule, of which AntJwphysa and 

 CephalotJwmnion are among the best-known examples. 



3. 'Cell- Wall. This stands in intimate relation with the proto- 

 plast, as in Algae and higher plants, so that the cell-body has no 

 independent movement, apart from the automatic streaming of 

 granules. The cell-wall may (Dinoflagellata) or may not (Volvo- 

 caceae and Coccolithophoridae) divide with the protoplast. Its 

 chemical composition resembles that of the perisarc, and in the Dino- 

 flagellata consists of cellulose. In the Coccolithophoridae the cell- 

 wall is built up of several shells 

 composed of calcium carbonate. 



Nucleus. The nucleus of the 

 Mastigophora shows many varie- 

 ties of intimate structure. In .A. 

 some cases the chromatin is dis- 

 tributed in the form of a simple 

 .chromatic network (Herpeto- 

 monas), in others (Bodo, Copro- 

 monas, Fig. 2) the chromatin is 



nrptjpnr in flip fnrm nf n opnfril Two sta 8 es in the mitosis of the nucleus 



mtrai of x oct n uca mmaris. A, archoplasmic body 



lump Or maSS. In Eugkna there < a > becoming elongated previous to division ; 



_.. i w > nucleus. B, the nucleus has wrapped round 



IS Within the nuclear membrane the central part of the archoplasmic body, and 



i , i the chromosomes (ch) are approaching the 



separate chromatin masses, and po ies in rows. (After CWklm.) 



in addition a substance which 



has been variously interpreted, but is usually known as the 



