Abstract
In a study of regeneration of form and function at various phases in the life history of the infusorians Spathidium spathula and Blepharisma undulans, it has been determined that the power of restoring lost parts and of continuing normal existence is in all cases dependent upon the same factor, the nuclear content of the fragment. Individuals of known pedigree were cut transversely, and the behavior or the fragments observed until regeneration and division or regeneration and death had occurred. During the vegetative state, regenerative power is highly developed in both ciliates, but because of the more distributed condition of the nucleus in Spathidium than in Blepharisma relatively smaller fragments from either extremity of the former are capable of complete regeneration. All fragments which continue to divide contain both macro and micronuclear material. It has been impossible to produce an amicronucleate race by artificial means. 1
In Spathidium, where the two nuclear elements extend throughout the cell both during and after fission, there is no difference in the regenerative power at any peroid of asexual life. In Blepharisma, however, where large amacronucleate fragments may be obtained during the process of division, it has been found that temporary restoration of external organelles is possible in the absence of nuclear material, if the formation of a new peristome has already been started. Dedifferentiation immediately follows and death occurs in a few days. The presence of micronuclei in such fragments, moreover, is not sufficient for continued existence.
During conjugation, complete regeneration in Spathidium is less frequent than during asexual life. Portions containing the synkaryon regenerate and divide; other pieces remain unchanged or undergo only temporary restoration of form. Fragments obtained from starved Spathidia prior to encystment either fail to regenerate, or regain normal form and subsequently encyst.
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