Volume 3, Issue 3
March 1936, pages 175-281
pp 175-194 March 1936
The oogenesis ofDasychone andSalmacis has been worked out from oocytes collected during two different seasons.
Changes in the physico-chemical factors of the Sea and the Adyar river water have been studied.
Measurements of the ripe oocytes indicate a cousistent increase in size in the oocytes ofClibanarius and a decrease inDasychone andSalmacis from January to June. It is presumed that these alterations in size are caused by variations in salinity.
In December-January preparations ofDasychone, fat—the only deutoplasmic inclusion—appears to be formed by the transformation of Golgi material.
In May–June fatty yolk alone has been observed in the eggs and this appears to be secreted by the dictyosomes.
The nucleoli and nucleolar buds are stained deep red in December–January while in May–June they are orange, of slightly varying shades.
InSalmacis also, there is a variation in the quantity of nutritive bodies, mitochondria and yolk in the two seasons.
An attempt has been made to show that the remarkable diversity of results obtained by workers on the same animal are due to variations in the environment: (1) seasonal, (2) geographical.
pp 195-211 March 1936
M. hebetov Say is recorded for the first time from North India and notes are given of its behaviour and hosts in Ceylon.
In India its usual host has not been discovered, it was discovered in a room where lac was stored, and was bred in the Laboratory as an ecto-parasite ofEublemma amabilis andHolcocera pulverea, both serious enemies of the lac cultivator.M. hebetor is believed to be rare in North India.
A preliminary detailed description of its bionomics, breeding and life-history is given: the hosts used wereE. amabilis, H. pulverea andE. scitula, the latter although occasionally a lac predator is a beneficial rather than harmful insect on account of its larval habit of feeding on injuriousCoccids. M. hebetor was induced to oviposit onPlatyedra gossypiella larvæ under laboratory conditions at Namkum.
The hosts of theBraconid in other parts of the world are all pests of varying importance, largely of stored products. Many of these pests occur in India.
The percentages of escapes, failures to oviposit and mortality among the life-history stages are rather high; these, it is considered, will be reduced with improved breeding technique and with acclimatisation toE. amabilis andH. pulverea as hosts. TheBraconid is considered to be a potentially ideal parasite for acclimatisation and introduction in lac-growing areas.
As no further specimens have been collected or obtained here, arrangements were made to obtain a consignment from Ceylon for further investigation; the consignment arrived safely giving a percentage of only 28·9% adults.
pp 212-213 March 1936
pp 214-233 March 1936
pp 234-237 March 1936
The genusDermatoxys Schneider, 1866, embraces three species:D. veligera (Rudoiphi, 1819) Schneider, 1866;D. getula Seurat, 1915; andD. polyoon Linstow, 1909. The species discovered by the writer of this paper differs markedly from the two last named species but in certain respects resembles the first named and is to be distinguished from it by the number and arrangement of the ventral caudal papilæ. Although the description ofD. veligera given by Schneider, Seurat, Hall and the figures given by Yorke and Maplestone all differ from one another in some respect or the other, yet none of the description is applicable to the species found inLepus ruficaudatus. This necessitates the creation of a new species and it is proposed to call itDermatoxys ruficaudata.
It is interesting to note that the cervical alœ in certain seciniens extend beyond the œsophageal bulb while in others they are shorter and end above it or terminate at the level of the œsophageal bulb. Hall has observed the first condition and repudiates Seurat’s statement that the cervical alæ inD. veligera terminate posteriorly at the level of the œphageal bulb. Yorke and Maplestone have mentioned that the cervical alæ extend from the head to the end of the sophagus but from the figure. given by them it appears that these end above the cesophageal bulb. The writer has observed all the three conditions in the material obtained by him and concludes that the length of the cervical ahe may differ in males and females, both of the same species.
pp 238-245 March 1936
The paper deals with the effect of varying concentrations of oxygen on the production of dry matter in plants. The following conclusions are the outcome of the present investigation:—
The dry matter produced is more or less proportional to the concentration of oxygen. With increasing percentages the curve merges into a stationary and later a decline phase.
The increased growth at higher concentrations of oxygen is explained on the basis of increase in the intensity of both respiration and assimilation. Suggestion is made that the former controls the production of dry materials probably by a control over the supply of energy, while the latter by controlling the development of the photosynthetic machinery.
The deviations in the concentration of Oxygen near about those of the atmosphere do not affect the dry matter production to any great extent, proving thereby that growth is not ordinarily limited by the concentration of oxygen under natural conditions of the plains and the critical concentration for the growth of wheat plants lies near about 15%.
The dry matter production at any stage appears to be a function of the interaction between two variables, the age-factor and the factor for oxygen. An increase in any one of these factors at any stage brings about increased growth showing thereby that under the conditions of experimentation growth in plants at any stage of the life-cycle is not limited by one factor alone but by as many as two factors,viz., the age-factor and the factor for oxygen.
pp 246-257 March 1936
pp 258-277 March 1936
Periodical observations on rice plants grown under wet as well as dry soil conditions, with and without different organic manures, showed that (a) better growth and yield are obtained under swamp conditions than under “dry” ones, (b) there is a greater intake of minerals particularly silicon in the case of the swamped series over that in “dry” series, and (c) the percentage of silicon in plants grown in the swamped and manured soil is greater than in the others.
The significance of these observations in relation to (a) the possible beneficial effects of silicate fertilisation in field practice, and (b) the rôle of silicon in the nutrition of the rice plant have been discussed.
pp 278-281 March 1936