PLASMODIOPHORALES 



ture may be cited to show that what had previously 

 been regarded as chromatin extruded from the nu- 

 cleus is now known to be chondriosomes, reserve, and 

 degenerative products of metabolism. Belar ('26) 

 thus characterized the present status of the chro- 

 midia theory as follows: "Die Lehre vom Chroma- 

 tindualismus steht und fallt mit einer unkritischen 

 P'assung des Cliromatinbegriffs, sie is das posthume 

 Produkt einer naiven Interpretation der histologis- 

 chen Fiirbung." In light of tliese more recent data 

 from the field of protozoology, Prowazek's, Claire 

 and Tison's, Blorafield and Schwartz's, Schwartz's, 

 Osborn's, Cook's, and Jones' interpretations of chro- 

 matin extrusion, chromidia, and the origin of the 

 generative nuclei in the Plasmodiophorales need re- 

 vision. 



Milovidov attempted to do so in a restudy of the 

 akaryote and nuclear reconstruction stages in Plas- 

 modiophora with the aid of mitochondrial fixatives 

 and Feulgen's nuclear stain. From these studies he 

 concluded that the so-called chromidia in the cyto- 

 plasm are nothing more than chondriosomal residue, 

 excretions, or secretions. He found that shortly be- 

 fore spore formation the plasmodium becomes quite 

 vacuolate and tliat chondriosomes and other bodies 

 may frequently lie within such vacuoles. This ap- 

 l^earance, according to him, is the basis for Schwartz, 

 Osborn, and Jones' claim that new nuclei arise de 

 novo in vacuole-like areas from extruded chromatin 

 granules. With Feulgen's stain such granules show 

 no positive chromatin reaction. As to the presence of 

 a marked akaryote stage with nuclei partly or com- 

 pletely devoid of chromatin, Milovidov discredited 

 previous workers and maintained that it does not 

 exist as a distinct developmental phase of the Plas- 

 modiophorales. He contended that the plasmodium 

 does not fix and stain uniformly throughout all of its 

 developmental phases, so that fixatives and stains 

 wliich give good preparations of one phase are un- 

 suitable for anotlier stage. In none of the properly 

 fixed and stained plasmodia did he find empty, vac- 

 uole-like nuclei. Instead, when so-called enucleate- 

 and akaryote-like stages described by previous work- 

 ers were stained by F"eulgen's method, the nuclei 

 were found to have numerous chromatic granules, 

 strands, and spireme-like threads, all characteristic 

 of meiotic projjhases. Milovidov thus concluded that 

 the akaryote and nuclear reconstruction stages of 

 earlier cytologists relate in part to artifact, as Miss 

 Terby had earlier pointed out, misinterpreted mei- 

 otic prophases and telophases, poorly fixed and 

 stained resting nuclei of vegetative plasmodia, and 

 abnormal nuclei of degenerating schizonts and plas- 

 modia. His contentions are supported to a great ex- 

 tent by the failure of Maire and Tison, Winge, 

 Terby, Home, Webb, and Ledingham to find marked 

 akaryote stages in Trtrami/j-a, Sorodixciis, Pla.smo- 

 diophora, Spoiif/oxpora, Soiosphaera, and Polymy.ra, 

 respectively. 



Meiosis 



It is now ratlier generally believed that meiosis oc- 

 curs during the last two divisions before or during 



cleavage into resting spores, and tliese divisions arc 

 respectively referred to as hetero- and homeotypic. 

 Nawaschin first noted these divisions in Plasmodio- 

 phora but reported only one mitosis before spore for- 

 mation. Prowazek ('05) found two mitoses, and since 

 that time two divisions have been universally re- 

 ported. Claire and Tison ('09) were the first to count 

 the chromosomes during these divisions in Soro- 

 sphaera, and because tlie number appeared to be 

 lialved in the first divisions they accordingly con- 

 cluded that these divisions are reductional. Tlieir 

 interpretation has been accepted by most subse- 

 quent workers. Exceptions to this view, neverthe- 

 less, may be found in the literature. Prowazek ('05) 

 reported that reduction in Plasmodiophora occurs 

 during maturation of the resting spores following 

 autogamy or a previous fusion of cleavage segments 

 or incipient spores. Winge contended that a numeral 

 reduction of chromosomes takes place in the second 

 instead of the first sporogonic division in Sorodisciis. 

 More recently Cook ('26, '28, '33) and Fedorintschik 

 ('35) reported a second reduction division in the zoo- 

 sporangia or gametangia of Ligniera and Plasmodio- 

 phora in addition to the one which occurs at sporo- 

 genesis. According to Cook ('33, p. 221). the two 

 reductions in Ligniera are necessitated by a double 

 fusion, one between "swarm cells" and tlic other 

 between zoospores. F'edorintschik reported only one 

 fusion in P. Brassicae. However, neither of these 

 workers counted the cliromosomes during the first 

 two divisions in the zoosporangia, and their conten- 

 tion that these divisions are meiotic is based solely 

 on the similarity in appearance of the latter to the 

 reduction divisions at sporogenesis. In Tetrami/xa 

 Elaeagni, Yendo and Takase ('32) reported tliat the 

 sporonts are haploid. which presupposes a reduction 

 before the plasmodium cleaves into spore mother 

 cells or sporonts. 



As noted before, most cytologists reported that 

 the vegetative meiotic divisions are separated by a 

 marked akaryote stage, but Terby, Home, Webb, 

 Ledingham, and particularly Milovidov failed to 

 confirm these reports. Thus, the latest data from 

 carefully fixed and stained material suggest tliat the 

 akaryote stage of the early workers relates in part 

 to an achromatic phase of the nucleus and partly to 

 the meiotic ])rophases. Prowazek's ('05) figures 17 

 to 22, for example, show chromatin reticula, loops, 

 garlands, spireme threads, and eight chromosome- 

 like bodies which are very characteristic of the mei- 

 otic prophases of later workers. 



Following the more or less achromatic transitional 

 phase, tlic nucleole and chromatin filaments of Soro- 

 sphaera, Plasmodiophora, and Spongospora, accord- 

 ing to Maire and Tison ('09), Terby ('24) and 

 Home, become more basophyllic and clearly visible 

 in tlie nucleus. At tlie same time sharply defined cen- 

 trosomes and asters apjjcar at tlie poles. The chro- 

 matin then aggregates at tlie poles into two more or 

 less dense masses, which may remain connected by 

 fine chromatic filaments. This is the so-called "gar- 

 land stage" of meiosis. Home found that each polar 



