Biological Studies Classic Reprint
Idioma: inglés
Editorial: Forgotten Books, 2019
- Tapa blanda
- Nuevo
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N° de ref. del artículo LW-9781330455517
- Título
- Biological Studies Classic Reprint
- Autor
- William Thompson Sedgwick
- Editorial
- Forgotten Books
- Año de publicación
- 2019
- Estado
- New
- Encuadernación
- PAP
- Idioma
- inglés
- ISBN 10
- 1330455517
- ISBN 13
- 9781330455517
- Peso del artículo
- 538 gramos
Paramecium aurelia, according to Maupas, differs from P. Cau datum in the following points: It is smaller (70 to 290 p, as against 120 to 32 5 p. In P. Caudatum); its posterior end is rounded, while P. Caudatum has an attenuated end (hence caudatum); it has two small micronuclei (3 to 5 u in diameter), while P. Caudatum has but one (8 to 10 u); in conjugation its macronucleus becomes rib bon-shaped at an earlier period than in P. Caudatum; and after conjugation its cleavage nucleus gives rise to four corpuscles, whereas in P. Caudatum there are eight. In deciding which of these forms to call caudatum and which aurelia, Maupas could not determine which type Miiller had seen, and went back therefore only to Ehrenberg, who' in naming P. Caudatum had noted the attenuated posterior end. Hence it turns out that the more common form of Para mecium has become widely known as P. Caudatum, while the less common form bears the original name P. Aurelia. If the two are only variants of the same species, it follows from the rules of zo ological nomenclature that the common and well-known name Para mecium caudatum must be given up and P. Aurelia substituted. That this must be the case follows, as I believe, from the observa tions here described. In the following description the names P. Caudatum and P. Aurelia will be used for those variants of the organ isms which agree with Maupas' Specific characteristics.
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This book is a reproduction of an important historical work. Forgotten Books uses state-of-the-art technology to digitally reconstruct the work, preserving the original format whilst repairing imperfections present in the aged copy. In rare cases, an imperfection in the original, such as a blemish or missing page, may be replicated in our edition. We do, however, repair the vast majority of imperfections successfully; any imperfections that remain are intentionally left to preserve the state of such historical works.
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Reseña del editor
At the present time, when the subject of mutations and species is discussed on every hand, and when every eye is keenly on the alert for new evidence among animals and plants, a sudden transformation of one known species into another known species is of interest. Such an incident has recently come under my observation; a Paramecium caudatum became P. aurelia, and remained so for about 45 generations, when it reverted to P. caudatum. Apart from the facts of the change, which in itself is of obvious importance from the standpoint of cellular biology, the essential question to consider is whether these two species are sufficiently well defined to justify their separation. If not, then the experiments and the changes indicated have less bearing on the general problem of mutation than upon the problems of cell physiology. If they are sufficiently distinct, then we have in this incident an interesting case of mutation. I personally believe that the slight differences that distinguish the two types of Paramecium are not of specific value, and hold that P. caudatum should be regarded as a mere variant of P. aurelia.
Paramecium aurelia was the name given by Müller, in his general work on the Protozoa in 1773, to the ciliated organism which had been known as the "slipper animalcule." Several different species of Paramecium were created by Ehrenberg in 1838, and described in his work on the Infusionsthierchen. Most of these have been sifted out into other genera, and only three have remained, P. bursaria, P. aurelia, and P. caudatum. Paramecium caudatum and P. aurelia have been united into a single species by the majority of observers subsequent to Ehrenberg, on the ground that the differences upon which Ehrenberg had based his species were inadequate. The number of species was thus reduced to two, and the names used were P. aurelia and P. bursaria, the former having been given originally by Müller.
About the Publisher
Forgotten Books publishes hundreds of thousands of rare and classic books. Find more at www.forgottenbooks.com
This book is a reproduction of an important historical work. Forgotten Books uses state-of-the-art technology to digitally reconstruct the work, preserving the original format whilst repairing imperfections present in the aged copy. In rare cases, an imperfection in the original, such as a blemish or missing page, may be replicated in our edition. We do, however, repair the vast majority of imperfections successfully; any imperfections that remain are intentionally left to preserve the state of such historical works.
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