185 SEX IN MICROORGANISMS 



Borgert (1900) made a study of the division stages of Aula- 

 cantha scolyviantha (Tripylea). In the mitoses he estimated about 

 1000 chromosomes. (Haecker, later, in 1906, estimated 1500 to 1600 

 chromosomes in Castanidhim variable). In 1909 Borgert extended his 

 study of nuclear division and described a quite different type of 

 development. In this, chromatin migrated out of the nucleus as small 

 units (Fig. R, 1, 2); these later became small nuclei which divided 

 mitotically with about 10 to 12 chromosomes (3 to 5). The central 

 capsule disappeared, and the cytoplasm became separated into many 

 "spheres" (6) of various sizes each containing many small nuclei (7). 

 Development of these nuclei was not followed, but Borgert believed 

 that the macro- and microspores were gametes and fused to produce 

 zygotes. No fusions were observed. 



It will be recalled that Brandt (1905) described anisospores that 

 resembled small dinoflagellates. Chatton (1920), in his monograph on 

 parasitic dinoflagellates, reviewed the literature dealing with sporu- 

 lation in Radiolaria and concluded that the anisospores were, in most 

 cases, parasitic dinoflagellates. He noted that anisospores were bean- 

 or kidney-shaped with a constriction or furrow at the equator from 

 which two flagella arose, and they had no "crystals." He believed 

 that the anisospores described by Brandt and the Schlaiichkemserie 

 flagellispores described by Huth were parasites. The facts that Huth's 

 Schlauchkernserie began development in the nucleus, then pushed out 

 into the surrounding endoplasm, and that they were at all times sur- 

 rounded by their own membrane, and that the contained nuclei ap- 

 peared to be in continuous division (Fig. Q, 18 to 21) indicated char- 

 acters corresponding to those of species of Syndinhmt that Chatton 

 had found parasitic in copepods. Although Chatton was unable to 

 observe any fusions among the "anisospores" of Syndiniii/n, he and 

 Biecheler (1936) later observed fusion between dinospores of slightly 

 different size in Coccidinmm mesnili, another parasitic dinoflagellate 

 (Fig. C, 9 to 12). Chatton was quite willing to admit that isospore 

 development and that in Huth's Spindelkernserie were part of the 

 life history of the Radiolaria. 



If Chatton's contentions are correct, we are left without any 

 sexual phenomena in the Radiolaria in the accounts reviewed up to 

 this point, since isospores were not thought to be gametes. However, 

 when we come to the study of Actipylea (Acantharia), the group 

 with skeletons of strontium sulfate, the story is somewhat different. 



