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Quarterly Journal of Microscopical Science, Vol s2-84, 295-328, Copyright © 1944 by Company of Biologists
1 Zoology Department, University of Glasgow
2 Laboratory of Notre Dame, Dowanhill, Glasgow
1. The discovery of a new species of large, free-living freshwater amoeba is recorded, and a description of the adult and of its reproduction is given. Although provisionally called Amoeba lescherae, it may have to be placed in the genus Chaos.
2. A method of cultivating it in the laboratory on a diet of small flagellates and ciliates subsisting on a pabulum of wheat grains is detailed. By starting them in Petri dishes pure line cultures are shown to be easily obtainable.
3. The resting nucleus, discoid in shape, has been shown to bear a general resemblance to that of Amoeba discoides as well as Amoeba proteus Y. Division is mitotic, and occurs once in twenty-four hours under optimum conditions. In contrast to Amoeba proteus Y the separation of the daughter amoeba is facilitated by the mechanical support of minute fragments of floating debris.
4. The cytoplasmic contents include square prismatic crystals, nutritive spheres, fat globules, neutral red bodies, and mitochondria.
5. It has been shown that while the adult has a general resemblance to Amoeba proteus Y the respective developmental stages of the two amoebae are in marked contrast.
6. Agametogony is seen to begin with the emission of ‘chromidia’ from the nucleus. These chromidia form the rudiments of the agametes which differentiate into cysts. Excystationis described.
7. Agametogonyoccurs morefrequentlyin Amoeba lescherae than in Amoeba proteus Y, the intervals between the ‘depression’ periods being shorter in the former than in the latter.
8. The development of the nucleus from the newly hatched amoeba to its adult condition has been traced, and the immature nucleus has been contrasted with that of species of Mayorella.
