THE SPOROZOA 



185 



Monocystis, but soon become differentiated. Those in the female 

 chamber are smaller (about 7'5 /x in diameter), without much 

 reserve material, and do not acquire any further structural 

 peculiarities (Fig. 30, e). Those in the male chamber are larger 

 and have more reserve material, and develop into motile gametes 

 with the following structure (Fig. 30, b, c, d). The body is fusi- 

 form or cylindrical, about 13 /x, in length, with an anterior clear 



e. 



PIG. 29. 



Schematic figures of conjugation and spore-formation in Gregarines, after Calkins, modified ; 

 the details of nuclear structure and division copied from Siedlecki's figures of Lankesteria 

 ascidiae (E. R. L.). a, union of two sporonts in a common cyst. 6, division of the nucleus of 

 each sporont, showing various stages of division by mitosis, with very distinct centrosomes 

 and without loss of the nuclear membrane. Fragments of the karyosomes are also seen, one on 

 the left, two on the right, c, commencing formation of gametes. The very numerous minute, 

 irregularly-shaped nuclei place themselves at the surface, and become segmented off, as seen 

 on the lower side of the sporont on the right. (In iMnkesteria ascMiae at this stage the sporonts 

 become very irregular in shape and drawn out in various directions.) rf, Stages in the con- 

 jugation of the gametes. In the left upper quadrant of the figure are seen separate gametes ; 

 in the left lower quadrant the gametes are seen uniting in pairs ; the right lower quadrant 

 shows the fusion of the nuclei ; and in the right upper quadrant are seen complete zygotes or 

 definitive sporoblasts. e, Stages in the division of the nuclei of the sporoblasts, which at the 

 same time assume an oval form. The division of the nucleus takes place by the direct method 

 into two, four, and eight small nuclei. /, cyst with ripe spores, each of which contains eight 

 sporozoites derived from the eight nuclei of the sporoblast. Two spores are seen in cross- 

 section. 



and a posterior granular extremity. The anterior end is prolonged 

 into a rostrum terminating in two little horn-like processes. The 

 posterior end bears a flagellum about 27 p. in length. The nucleus 

 is at the anterior pole of the body and consists of chromosomes 

 not enveloped in any membrane. The flagellum is continued from 

 the base forward through the body of the gamete as a delicate 



