Studies on the Life History of Blepharisma undulans.

Abstract

Studies on the life history of Blepharisma undulans have been in progress for over five and a half years, all the animals employed being the progeny of a single individual isolated November, 1921. The work was planned to determine, in particular, the viability of this infusorian in the absence of fertilization, and the effects of fertilization on the rate of reproduction, in an attempt to broaden the results from our earlier studies on Paramecium aurelia 1 and Spathidium spatula. 2 A preliminary statement of the characteristics of this race of Blepharisma undulans was presented in 1922. 4

Whereas earlier workers on this organism found that conjugation occurred rather infrequently and invariably was followed by death, conjugation was readily induced in our pedigree cultures, and the exconjugants proved to be viable in nearly every case. Accordingly excellent material was afforded for the problem at hand.

Two conclusions may be emphasized from the data secured to date:

(1) The animals of this race of Blepharisma undulans may reproduce apparently indefinitely without recourse to conjugation; there being no “cycles” in the vitality of the organism, as evinced by the division rate or otherwise, which terminate in death when fertilization is prevented.

(2) Animals isolated from a pedigree line and allowed to conjugate immediately show a markedly higher rate of reproduction than that of the parent line, and this accelerated division rate is maintained for at least thirty clays and, usually, until the experiment is discontinued.

In brief, the conclusions derived from Paramecium 1 and Spathidium 2 , 4 that these infusorians are capable of unlimited reprodulction, under favorable environmental conditions, without recourse to fertilization may now be extended to Blepharisma; and, furthermore, the conclusion that fertilization accelerates the division rate, as previously demonstrated in Uroleptus 3 and in Spahidium, 2 may now be extended to Blepharisma.