142 



PROTOZOOLOGY 



of network (c); at this stage, the cytoplasm around the nucleus is 

 much vacuolated. A little later appears a discoid equatorial plate or 

 ring which is connected with the nuclear membrane by numerous 

 fibrils, and the nucleus becomes markedly flattened with its mem- 

 brane still intact (d), which is considered as the end of the prophase. 

 In the metaphase, the nuclear membrane becomes extremely faint 

 and the portion over one side of the plate is without it (e). At the 



Fig. 65. Nuclear division in Amoeba proteus, Xl80 (Chalkley and 

 Daniel), a, resting stage; b-d, prophase; e, metaphase; f, g, anaphase; 

 h, a daughter nucleus. 



anaphase the membrane completely disappears, the equatorial plate 

 splits and each half contracts in the plane of the plate, producing 

 two daughter-plates. In some specimens a faint spindle formation is 

 noted. At about this time, vacuolated condition of the perinuclear 

 cytoplasm disappears (/). In later phases of anaphase the plates are 

 more widely separated and are slightly less in diameter as compared 

 with earlier stages. There are distinct polar caps of fibrillar material 

 at the poles of the spindle (g) , fi.nally each plate transforms itself into 

 a resting nucleus (h). The two investigators added that if the chro- 

 matin granules located in the equatorial plate are chromosomes, 

 "they must be extremely numerous." Liesche (1938) estimates the 

 number of these granules which he called chromosomes as between 

 500 and 600. 



