OPALINID CILIATE INFUSORIANS — METCALF 621 



Konsuloff, 1930, discussing the nuclear nature of the endospherules, 

 said that these disk-shaped bodies are macronuclei, are permanently 

 formed structures, have an evident, thick membrane, divide without 

 chromosome formation, disappear during the sexual process to reap- 

 pear later. He [erroneously] says that de Meyer and also Metcalf 

 would have accepted the macronuclear nature of the spherules if 

 they had beheved that the spherules divide, a conception for which 

 Konsuloff and especially Horning (1937) give evidence. [Not so. 

 The macronuclei of eucihates are true nuclei, derived from micro- 

 nuclei. This cannot be true of the endospherules of opalinids. They 

 may possibly be composed of, or derived from, metabolic chromatin, 

 as Metcalf, 1909, suggested (cf. Reichenow, 1928), but they are not 

 metamorphosed nuclei.] 



At the Christmas meetings of the American Society of Zoologists 

 in New York City in 1928 Kofoid and Dodds reported work upon 

 Opalina obtrigonoidea and 0. virguloidea. The abstract of their revo- 

 lutionary paper is quoted here. "Mitosis in the two species has been 

 studied. At nuclear division an extranuclear centrosome divides and 

 the daughters migrate to the poles of the elongating nucleus, forming 

 an extranuclear paradesmose, as in the flagellates. Each nucleus has 

 a slender rhizoplast running from the centrosome on the periphery 

 of the nuclear membrane to a basal granule — in reality the blepharo- 

 plast — from which the flagellum, the so-called cilium, emerges. From 

 the blepharoplast another rhizoplast runs down to the so-called endo- 

 plasmic spherules, which are interpreted by us to be parabasal bodies. 

 The unit of the neuromotor system in the species observed thus con- 

 sists of the following parts: the flagellum, its blepharoplast, parabasal 

 body and its rhizoplast, and, if attached to a nucleus, the rhizoplast 

 running from the blepharoplast to the centrosome on the nuclear 

 membrane. The blepharoplasts are arranged in spiral lines and the 

 parabasal bodies are distributed below them less clearly showing the 

 spiral arrangement. The neuromotor units are thus considerably in 

 excess of the number of the nuclei. A similar relation has been 

 evolved in a number of multicellular types of flagellates found in the 

 termites, in which, as in the genus Calonympha, there are more neuro- 

 motor units than there are nuclei. The neuromotor system and the 

 type of mitosis in the opalinid Protozoa are clearly homologous to 

 that of the flagellates. In the light of these facts, it is logical to trans- 

 fer the Opalininae from the Ciliata to the Flagellata." [Publication 

 in full must precede adequate criticism, but we may note: (1) that 

 no other students have shown centrosomes, even after prolonged 

 search by a great variety of techniques; (2) that the appearance of a 

 longitudinal fiber upon the caryotheca of the dividing nucleus is 

 occasionally seen, especially in the living animal, but prolonged 



