. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. Vol. 86, No. 3 V^/s^^»2>/^O*y June, 1944 THE BIOLOGICAL BULLETIN PUBLISHED BY THE MARINE BIOLOGICAL LABORATORY PARAMECIUM BURSARIA: LIFE HISTORY. I. IMMATURITY, MATURITY AND AGE 1 H. S. JENNINGS (University of California at Los Atuiclcs} INTRODUCTION The discovery of mating types or sex types in the ciliate infusoria has made it possible to breed and cross these Protozoa as readily as higher organisms. This has made possible under favorable conditions a renewed study of the problems of youth, age and death, particularly i
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. Vol. 86, No. 3 V^/s^^»2>/^O*y June, 1944 THE BIOLOGICAL BULLETIN PUBLISHED BY THE MARINE BIOLOGICAL LABORATORY PARAMECIUM BURSARIA: LIFE HISTORY. I. IMMATURITY, MATURITY AND AGE 1 H. S. JENNINGS (University of California at Los Atuiclcs} INTRODUCTION The discovery of mating types or sex types in the ciliate infusoria has made it possible to breed and cross these Protozoa as readily as higher organisms. This has made possible under favorable conditions a renewed study of the problems of youth, age and death, particularly in relation to conjugation. These problems form the subject of the investigation of which a first installment is presented here. The unit for examination in such studies is the clone rather than the single cellular individual. We deal with youth, age and death of clones, not of single cells only. The clone consists of all individuals derived by vegetative fission from a single ex-conjugant. The age of the clone is properly reckoned from the time of separation of the two ex-conjugants of the ancestral pair. A number of investigators, beginning with Maupas (1888, 1889) have reported that there is, following the separation of the conjugants, a period of immaturity, during which multiplication by fission occurs, but conjugation does not occur. This is followed, according to these reports, by a period of maturity during which con- jugation may occur. The period of maturity is said to be by a period of decline or degeneration, often spoken of as age or senescence. According to Maupas (1888) conjugation during this period of decline results in the death of the conjugants. The decline itself, without conjugations, also ultimately results in death. G. N. Calkins was long the outstanding representative of this general con- ception of the life history of the ciliate, though he did not. I believe, report that conjugation during the period of decline results in death. However, a n
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
