SEX IN PROTOZOA 185 



giving tlicin the appearance of certain dinoflagellatcs, like Gymno- 

 d'ni'mvt (10 to 13). In 1885 he had seen similar spores in Sphaerozoum 

 pimctiitimi (6 to 9). The nuclei of the two kinds were also different. 

 He believed that the two kinds of anisospores were produced by the 

 same parent. They emerged separately, then mingled together. He 

 never saw any pairing, but he did not put flagellispores from different 

 jiarents together. 



Huth (1913) made an extensive study of ThalassicoUa, mostly 

 T. spuviida and T. micleata. He described two different series of 

 developments, the Schlauchkernserie , which led to the formation of 

 microspores (Fig. Q, 18 to 22), and the Spiudelkernserie, which re- 

 sulted in macrospores (23). During development of the spindle series 

 there was a great increase in the size of the animals and the size of 

 the central capsule. The latter increased approximately a hundred- 

 fold in volume and the nucleus grew proportionately. During the 

 later stages the nucleus became lobulated, then broke up into spindle- 

 shaped areas, each with one or more nuclei. Further nuclear divisions 

 resulted in large numbers of nuclei, but the spindle-shaped areas dis- 

 appeared, as did the old nucleus itself. The very numerous small 

 nuclei became rather uniformly distributed throughout the capsule 

 and eventually, each with a small amount of cytoplasm, became a 

 macrospore (23). 



In the Schlauchkernsene a similar growth of the animals took 

 place (Fig. Q, 18 to 20). Groups of small nucleus-like bodies formed 

 in the large nucleus, these groups being surrounded by a membrane, 

 giving them a tubular appearance. These tubes grew through the 

 nuclear membrane out into the surrounding endoplasm (18). As they 

 grew, they split up (19) and eventually occupied most of the space 

 in the central capsule (20). In these "tubes" mitoses showing a rela- 

 tively small number of chromosomes seemed to be continually taking 

 place (21). Eventually microspores (22) were formed. 



Fig. R. Stages of "sporulation" in the radiolarian, Aulacmitha scolymantha, 

 from Kuhn (1926), after Borgert (1909), redrawn. 



1, early stage of dissolution of "primary" nucleus, small chromatin bodies ("sec- 

 ondary nuclei") appearing in endoplasm; 2, endoplasm full of "secondary" nuclei, 

 mere remnant of "primary" nucleus; 3, "secondary" nuclei when first seen in 

 endoplasm; 4, "resting stage" of "secondary" nuclei; 5, mitoses of "secondary" 

 nuclei; 6, break-up of cytoplasm into "spheres" or various sizes; 7, one of the 

 "spheres" enlarged to show many nuclei. 



