2/8 



REDUCTIOX OF THE CHROMOSOMES 



earlier divisions the number is aj^proxiniately double this (8-9). This 

 observation makes it nearly certain that a numerical reduction of 

 chromosomes occurs in the Protozoa in a manner similar to that of 

 the higher forms ; but the reduction here aj)])ears to be deferred until 





J 



\ 



^\^J v.^/ o>' 



A 



C 



Fig. 138. — Conjugation and formation of the polar bodies in Actinophrys. [SCHAUDINN.] 



A. Union of the gametes; first polar spindle. /?, Fusion of the cell-bodies; a single polar 

 body near the periphery of each. C. Fusion of the nuclei. 



the final division. In the gregarines Wolters ('91) has observed the 

 formation of an actual polar body as a small cell segmented off from 

 each of the two conjugating animals soon after their union ; but the 



number of chromo- 

 somes was not deter- 

 mined. Schaudinn 

 ('96, 2) has observed a 

 like process in Acti- 

 iwpJuys, each of the 



gametes 



segmentmg 



A 



C 



B 



D 



off a single polar body, 

 after which the germ- 

 nuclei fuse (Fig. 138). 

 It is ])ossible, as R. 

 Hertwig ('98) points 

 out, that in both these 

 forms a second ])olar 

 body may have been 

 overlooked, owing per- 

 haps to its rapid dis- 



Fig. 139. — Formation of polar bodies and conjugation in HltCgration. \\\. ActlllO- 



AcunosphcBrtum. [R. hertwig.] spha^riuvi, accordiug to 



A. Two gametes ("secondary cysts"), resulting from the p tt • /' o \ fU 



division of a "primary cyst"; second maturation-spindle in rierLWlg ^ 9*^ A '-^^ 



each; first polar bodv shown in the right gamete, at/. B. Both nuclcUS of Cach gamete 



polarbodies(/»i;>2) formed in the right gamete the second |- -^ ^ • • -^ 



one formmir m the left gamete. C. Subsequent fusion of the ^ 



gametes; nuclei uniting, two polar bodies (probably the second. SUCCeSSion tO form tWO 

 the first having been absorbed) at/. D. The young AcfinospAcF- 

 num escaping from the cyst-wall; the cleavage-nucleus has 



the first having been absorbed) at/. D. The yonng Actinosphce- t-)q]ot- bodies (^nnrlei^ 



divided. 



which degenerate, after 



