. The biology of the protozoa. Protozoa; Protozoa. 308 BIOLOGY OF THE PROTOZOA in the protoplasm. The cell then divides into as many daughter cysts as there are nuclei and these Hertwig calls cystospores No. 1, each of which secretes a gelatinous envelope about itself. The nucleus then divides by mitosis followed by division of the cell into two daughter cells which he calls cytospores No. 2. The nuclei of the latter undergo two successive "maturation" divisions resulting in one pronucleus and two "polar bodies" in each (Fig. 156), the latter degenerating and disappearing.
. The biology of the protozoa. Protozoa; Protozoa. 308 BIOLOGY OF THE PROTOZOA in the protoplasm. The cell then divides into as many daughter cysts as there are nuclei and these Hertwig calls cystospores No. 1, each of which secretes a gelatinous envelope about itself. The nucleus then divides by mitosis followed by division of the cell into two daughter cells which he calls cytospores No. 2. The nuclei of the latter undergo two successive "maturation" divisions resulting in one pronucleus and two "polar bodies" in each (Fig. 156), the latter degenerating and disappearing. The two cytospores of the second order now unite again, reforming cytospores No. 1 and fertilization is completed by fusion of the pronuclei. Belaf quite recently (1922) has given a more complete description of. Fig. 156.—Actinosphaerium eichhornii. A, two gametes ("cytospores No. 2") resulting from the division of the same mother-cell; B, both "polar bodies" are formed in the right gamete, the second one forming in the left gamete; C, the cell bodies of the gametes have fused, and the nuclei are fusing; D, young organism leav- ing cyst; p, p1, p2, " polar ; (After Hertwig.) the process in the allied form Actinophrys sol. The individuals draw in their pseudopodia, ordinary vegetative division of the nucleus follows, and the cell divides into two. By this division which Belaf terms the "progarnous" division, the two gametes are formed and after each of them has undergone two meiotic divisions of the nuclei they reunite to form the zygote. One of them anticipates the other in these divisions and develops a pseudo- podial process which the other lacks. By this process the first fusion of the two cells takes place. The original cell thus is a gamont and the fusing gametes are sister cells, one of which shows an incipient sex difference in its precocious activity and by its pseudopodium-like process. (Fig. 142, p. 27S.) There are 44.
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