Racial variations in Blepharisma undulans

Studies on Blepharisma undulans and Blepharisma lateritia Stein, have emphasized the impossibility or great difficulty of observing the micronuclei, and also the inevitable death of ex-conjugants without dividing. Thus Bütschli 1 was unable to identify micronuclei in vegetative specimens of B. lateritia though he found them in conjugants. Exconjugants invariably died. Calkins 2 did not find micronuclei in non-dividing B. undulans, but discovered them during division within the macronuclear membrane, and described their emergence and activities during conjugation. He likewise was unsuccessful in obtaining a single viable exconjugant.

During the past five months we have had under observation a pedigree culture of Blepharisma undulans which emphasizes racial differences within the species. The animals of this race possess from four to fourteen relatively conspicuous micronuclei, all of which are free in the cytoplasm during every stage of the life of the cell; and all the exconjugants thus far secured proved to be viable.

The main culture has attained one hundred and fifty generations to date, an average of about one division per day, in the standard beef extract culture medium used in this laboratory. At intervals, epidemics of conjugation have appeared. Exconjugants have been isolated and new lines established from their progeny. Studies are in progress similar to those which have been conducted on Spathidiums. 1

The wide experience of such observers as Bütschli and Calkins precludes the assumption that they were in error in regard to the micronuclear condition of the animals which they studied and the only reasonable conclusion is that there are races of Blepharisma which differ in regard to the vegetative position of the micronuclei; in some it is intramacronuclear and others extramacronuclear-the present pedigree race of Blepharisma undulans representing the latter and therefore agreeing with the marine species, Blepharisma clarissima, as described by Anigstein. 2