Paramecium polycaryum,sp. nov

Abstract

The several species of the genus Paramecium naturally fall into two groups: one with the general cell form represented by P. aurelia, P. caudatum, and P. multimicronucleata (aurelia group), and the other by P. bursaria, P. putrinum and P. calkinsi (bursaria group). Within each of these groups the species are distinguished chiefly by micronuclear structure and number. One type of micronuclear structure (caudatum type) occurs in P. caudatum and P. bursaria, and P. putrinum; the other (aurelia type) in P. aurelia, P. multimicronucleata and P. calkinsi. Species with the “caudatum type” possess a single micronucleus while those with the “aurelia type” possess two (P. aurelia, P. calkinsi) or several (P. multimicronucleata). 1

The present paper records the discovery, on November 29, 1922, in some material collected in Louisiana, of a Paramecium characterized by the general body form of the “bursaria group” and the micronuclear structure of the “aurelia type,” but possessing several (three to eight) micronuclei. In brief, the organism is essentially identical in form and structure with P. calkinsi, but has more than two micronuclei. Thus from the standpoint of micronuclear structure and number this animal holds the same position in the “bursaria group” as P. multimicronucleata in the “aurelia group.”

Pedigree cultures from the original animal found have now been under observation and experimentation for nearly four months, and through upward of one hundred and fifty generations. During this time the animals have bred true, exhibiting the characteristic micronuclear number after emerging from the nuclear reorganization involved in endomixis.

In view of all the above data the animals of this culture are designated a new species, Paramecium polycaryum. 2