Abstract
LONDON. Royal Society, January 24.—H. G. Cannon: On the development of an estherid crustacean. The ventral mesoderm of the estherid larva develops a transient segmentation that becomes obliterated by growth. Later, the more dorsal mesoderm develops a series of seven pairs of coelomic pouches. From the walls of these pouches are developed the dorsal longitudinal extensor muscles, and, in addition, from the first four, the muscular heart-tube. After these have been formed the cavities diminish in size. The space so formed between them and the ectoderni becomes the pericardial cavity. The lower edges of the sacs break connexion with the more ventral mesoderm, except in the maxillary segment, and grow downwards to form lateral portions of pericardial floor. The collapsed remains of the sacs are finally represented by pericardial floor and epithelial covering to the muscular heart-tube. The sacs do not in any way open into the general body-cavity. The genital rudiment is represented in the earliest larva by a paired mass of cells between mesoderm and endoderm. Later, it becomes included in the crelomic sac of the first trunk segment and grows backwards on each side as a rod, at first solid, of cells in the pericardial noon.—C. Shearer: The oxygen consumption rate of parts of the chick embryo and fragments of the earthworm. For equal quantities of tissue under similar physical conditions, the head tissue of the embryo consumed two to eight times more oxygen, measured by the differential manometer, than the corresponding trunk and tail portion of the embryo taken together. The oxygen consumption for a given quantity of tissue is highest in the fourth-day stage, the earliest investigated, and lowest in the tenth-day stage, the latest examined. A measurable quantity of oxygen is taken up by acetone powders, prepared by fixing head and tail portions of a large number of chick embryos in acetone for a week or more, and then thoroughly drying the fixed tissue and reducing it to a fine powder. Again the head portion took up most oxygen. Similar experiments were carried out on the earth-worm, using the Haldane manometer. About 3 cm. of head and tail portion of an almost fully grown starved earth-worm was used. The head region consumed again from two to five times more oxygen than the corresponding tail region of the worm.—N. Annandale: The evolution of the shell-sculpture in fresh-water snails of the family Viviparidae. Details are given of the evolution of prominent shell-sculpture in three series of species of Viviparidae, namely, (i) in those of the genus Tulotoma, from the Pliocene of Eastern Europe and the Levant; (2) in those of the living and tertiary genus Margarya, in Yunnan; and (3) in those of the living and tertiary genus Taia, on the Shan Plateau of Burma. Each series arose independently, and generic differences exist (or existed), not only in the shell, but also in the anatomy of the three genera. As regards species of Taia, the three forms which live in the Inle Lake, in the Southern Shan States, differ not only in their shells, but also in anatomy and in fertility. Each form is confined to a particular habitat, and one (T. intha), which inhabits the clear waters of the lake, is not only the most highly and regularly sculptured, but also the most constant in shell-characters and, in spite of the fact that it is extremely abundant, the least fertile. The last character is associated with lack of competition.—B. Sahni: Tmesipteris Vieillardi Dangeard: an erect terrestrial species from New Caledonia.—P. A. Buxton: Heat, moisture, and animal life in deserts. The surface temperature of Palestine at midday in summer is 55°-62° C. Insects exposed on the hot desert surface are less hot than might be supposed, e.g. a grasshopper's internal temperature was 40° C. and the surface on which it crouched 44° C., though insect and surface were alike in colour. A dead insect is hotter than a live one, and it appears that the cooling of the live insect is due to water lost in respiration. About eight insects can endure the Palestine summer sun at midday on bare ground; one of these is black. Fragments of dead annual plants, collected even in the middle of summer, contain 50-60 per cent, of water. Moreover, if these fragments are dried to constant weight and then exposed for periods of 24 hours in atmospheres of increasing relative humidity, they gain very little water until they reach the 70 per cent, humidity; from then onwards the gain is increasingly rapid. If, therefore, the dried fragments of annuals are exposed to a relative humidity of more than 70 per cent, at night (as constantly happens in nearly all deserts) they become actively hygroscopic and provide an unsuspected supply of water to all the desert animals in summer.—A. W. Bellamy and C. M. Child: Susceptibility in amphibian development.
Article PDF
Rights and permissions
About this article
Cite this article
Societies and Academies. Nature 113, 182–184 (1924). https://doi.org/10.1038/113182a0
Issue Date:
DOI: https://doi.org/10.1038/113182a0