from The American Heritage® Dictionary of the English Language, 5th Edition.
- noun Biology The occurrence of two or more distinct forms, as of an organism during its life cycle or of cells of a certain type.
from The Century Dictionary.
- noun Same as
- noun Same as
from the GNU version of the Collaborative International Dictionary of English.
- noun (Crystallog.) The property of crystallizing under two or more distinct fundamental forms, including
- noun (Biol.) The theory that the various genera of bacteria are phases or variations of growth of a number of Protean species, each of which may exhibit, according to undetermined conditions, all or some of the forms characteristic of the different genera and species.
from Wiktionary, Creative Commons Attribution/Share-Alike License.
- noun biology the
occurrenceof multiple structural formsduring the life cycleof an organism
- noun chemistry
from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
- noun (chemistry) the existence of different kinds of crystal of the same chemical compound
- noun (biology) the appearance of two or more distinctly different forms in the life cycle of some organisms
from Wiktionary, Creative Commons Attribution/Share-Alike License
However, the whole concept of "pleomorphism," although seeming plausible for a while in the late 19th century based on the limited knowledge of microbiology then, was long ago discredited, as
From that time the question of the pleomorphism (mutability of shape) of the bacteria has been hotly discussed: but it is now generally agreed that, while a [v. 03 p. 0158] certain number of forms may show different types of cell during the various phases of the life-history,  yet the majority of forms are uniform, showing one type of cell throughout their life-history.
The question, What is an individual? has given rise to much difficulty, and around it many of the speculations regarding pleomorphism have centred without useful result.
Zopf in 1885 proposed a scheme based on the acceptance of extreme views of pleomorphism; his system, however, was extraordinarily impracticable and was recognized by him as provisional only.
This variation in morphology is known as "pleomorphism."