CYTOI.OUY 



mcrly as |)romitt)sis in protozoa, fimu;i. and aljiaf 

 have provin to lie tyi)ical mitosis. 



NcvtTtlulfss. stmli-nts of tlit- I'lasmodiopliorales 

 ininu-diatcly rt-c-ognlzcd tin- similarity of Niiglfr's 

 jironiitotif divisions in Amoeba to tliosi- in tliis vt-jjo- 

 tativf Plasmodium, and in 1!)11 Main- and Tison 

 adopted Niiirlcr's tt-rni as descriptive of these Latter 

 divisions. Sulisecpient workers, ineliidiiiu: Cook (''Jii, 

 "28. '33), Cook and .Seliwart/, (,'-'!). ;}()). I.edingliam 

 ('39). and Coueli <■( al. ('39) have used the term 

 protoniitosis. a variety of promitosis described by 

 Alexieff. Pavillard ('10). Wcrnham ('35). and oth- 

 ers have employed the term "cruciform" division. 

 Althousth they fijjured the same tyjie of division. 

 Neniec ('11. '13), l-'erdinandscn and Wins;e ('20), 

 and Milovidov ('31, '32. '33) avoided extensive use 

 of these terms, while Osliorn ('U) described the 

 ve!i:etati\c division in Spoiif/o.spora as amitotic. His 

 figures and deserijition of the jirocess are nonetheless 

 similar to those of previous and subsequent workers. 

 Favorski objected to the contention that promitosis 

 is specifically characteristic of primitive animals and 

 the lMasniodioi)horaceac and [lointed out that the 

 karyosome and eliromatin may behave in a similar 

 manner during mitosis in hisjlier ))lants. Terby ('32) 

 likewise condemned tlie use of promitosis for these 

 divisions in Plasmndiophura on the grounds that 

 chromosomes are present and the daugliter nucleoli 

 are formed anew from granules in the telophase nu- 

 clei and not by division of a mother nucleole. Home 

 ('30) and Webb ('3.5) also contended that the vege- 

 tative divisions are tyjjically mitotic in Spongospora 

 and Suro.sphaera and thus contradicted all previous 

 workers who m.iintained that distinct chromosomes 

 are not )irescnt. 



Two main view))oints have thus been ])resented by 

 these cytologists : one that the vegetative divisions 

 are premitotic and fundamentally similar to those in 

 certain amoebae: the other that they are typically 

 mitotic with well-defined cliromosomes. Prowazek, 

 Maire and Tison. .Schwartz, and Cook in ])articular 

 have cmi)hasizcd the former view, and their accounts 

 of the vegetative divisions may be taken as represen- 

 tative of those who held that these mitoses are quite 

 unlike anything present in other fungi and higher 

 plants. Terby, Home, and Webb may be looked upon 

 as re])resenting the other viewpoint. For the sake of 

 com))arison. drawings representative of both views 

 have been brought togetlier in Plate I and contrasted 

 in turn with those illustrating jjromitosis in certain 

 amoebae. 



The resting nucleus of amoebae and i)l;ismodia of 

 the Plasmodioi)horaceae is quite small, so that its 

 structure is difficult to see and determine with cer- 

 tainty. Nawaschin described the chromatin in Plas- 

 mod iipliDra as a s])Oiigy. faintly-stainable reticulum 

 tliroughout the nucleus, while Prowazek figured the 

 nuch-i as having an alveolar achromatic structure 

 with several interspersed granules and a large cen- 

 tral nucleole lying in a clear zone. In other nuclei the 

 achromatic material was found to be radially ori- 

 ented on the nucleole (fig. 1). giving the nucleus a 



wheel-like a))|)earance. Fn Hi>ri>iij>hafia .-ind 'I'l-tra- 

 iiu/.ra, Maire and Tison figured tiie rt'sting nucleus as 

 devoid of a chromatin reticulum (fig. 2) with the 

 nucleole lying in a \ acuole-like ele.ir sp.iee filled with 

 hyaloplasm, and numerous granules distributed on 

 the inner periphery of nuclear membrane. They 

 ( '09) did not, however, regard these granules as true 

 I lirom.itin but instead as secretory chromidia derived 

 t'riiui the karyosome .-iiul destined to ))ass out into the 

 i\toplasm. In Spoiii/oxporu, on the other hand. Os- 

 liorn figured .1 wheel-like nucleus with numerous 

 chromatin granules distributed on radially oriented 

 liniu threads (fig. !•), but he likewise believed that 

 these granules had been derived from the karyosome. 

 Of the more recent workers. Cook, and Cook and 

 Schwartz have maintained that in Ligniera and Plax- 

 mod'iophora the chromatin is aggregated solely in a 

 layer around tiie inner i)eripliery of the nucleus 

 (fig. 5) with the result that the nucleole ai)i)ears to 

 lie in a clear vacuolate s))ace. but their observations 

 have not been confirmed. Cook's ('28) studies on 

 Lif/tiiera, however, were made from unsectioned ma- 

 terial stained in toto, which is obviously unfavorable 

 for study of nuclear details. 



Although there is thus considerable difference of 

 opinion among these cytologists as to the structure of 

 the nucleus and the presence of a chromatin reticu- 

 lum, the "wheel" tyiie of resting nucleus neverthe- 

 less has been figured most often and shown to occur 

 in Plasmodiophora, Sponr/ospora, Soros pharra, Lif/- 

 niera, Sorodiscus, and Polifmyxa. Milovidov's ('32, 

 '33) observations on resting nuclei of P. Brassicae 

 stained by Feulgen's method are particularly jierti- 

 nent in this relation. In such prei5arations the karyo- 

 some. linin. and granules are colorless, and the only 

 visible structure is the faintly-stained luiclear mem- 

 brane. Milovidov, nonetheless, believed that small 

 chromatin bodies are present around the inner peri- 

 phery of the nucleus. 



According to Nawascliin. the early ])rophases of 

 the vegetative divisions in Plasmodiophora may be 

 recognized by the emergence of distinct granules in 

 the nucleus (fig. (5) wliich have a markedly different 

 staining reaction from the karyosome and are not in 

 genetic connection with the latter. Their origin is 

 quite distinct from that of the karyosome, in Nawas- 

 chin's o))inion. These granules later unite and form 

 an equatorial ]jlate or band. Newaschin's observa- 

 tions were confirnied by Milovidov's ('32, '33) 

 studies which involved Feulgen's nuclear reaction 

 method. As the nuclei enter the )iro))hases. chromatin 

 granules and threads become visible in the nuclear 

 cavity, and these eventually form an equatori.d ring 

 (fig. .50). Prowazek ('0.5), on the other hand, de- 

 scribed the karyosome or "Inncnkorper" as enlarging 

 and difl'erentiating into a faint-staining achromatic 

 substance and a denser chromatic material (fig. 7). 

 The l.itter sul)stance then separates into a globular 

 luiclcole and a half moon-shaiied row of granules 

 (fig. 8), out of which the equatorial ring is formed 

 (fig. 9). Maire and Tison ('09), like Nawaschin, 

 noted the emergence of gramdes on the linin threads 



