Volume 2, Issue 2
August 1935, pages 137-235
pp 137-154 August 1935
pp 155-174 August 1935
A brief description of the foregut inPenœus indicus and a comparative account of the same in the remaining types of Penæidea and Stenopidea examined by me has been given.
The structure of the gastric mill in the Decapoda conforms to a typical plan common to all species, the variations being due to the coalescence, reduction or disappearance of one or more ossicles; in those forms in which the gastric mill is reduced the homologies of the principal ossicles can be made out.
The various types of the gastric mills found in the Decapoda can be arranged in a series ranging from simple to complex.
The forms considered as “primitive” for taxonomic and other reasons possess a simple type of gastric mill as compared to the gastric mills in the more “advanced” forms. The evolution of the gastric mill closely follows the evolution of the Decapoda.
The efficiency of the gastric mill is correlated with the efficiency of the external masticatory apparatus, chiefly the mandibles, the mandibles being simple in the forms in which the gastric mill is complex andvice versa.
The reason for the presence of the internal masticatory apparatus in one case and of the external masticatory apparatus in the other can be found in the habit and habitat of the animals. Reptantous habit is associated with the possession of a complex gastric mill and simple mandibles and the Natantous habit, on the other hand, with the possession of a reduced gastric mill and complex mandibles.
pp 175-201 August 1935
pp 201-212 August 1935
When a solution of sodium silicate is added to hydrogels of iron oxide or alumina there is considerable adsorption of silicate similar to that observed in the case of the soil. Retention of silica is greater in the case of alumina than with iron oxide gel and the percentage retention decreases with increasing concentration.
Similar adsorption of silica occurs in the case of ferric, or aluminium hydroxide gel—silica sol systems.
Study of the influence of hydrogen-ion concentration on extent of silica retention shows that as the PH of the medium increases, there is a decrease in the retention of silica by the gel. With alumina gel at high PH, however, there is greater adsorption. This is due to the amphoteric nature of alumina.
The adsorbed silicate is firmly retained by the colloidal gel and is not leached out by water.
The possible significance of silicate adsorption in relation to phosphorus resorption in soils is indicated.
pp 213-235 August 1935