298 SUMMARY OF CUERENT RESEARCHES RELATING TO 



margaritifera Dupuy. At the Colonial Exhibition at Marseilles, in 1906, 

 Auguste Lumiere, at the request of Dubois, made and exhibited a 

 fine radiograph of a pearl in a valve of 31 ar gar it if era vulgaris Jameson. 



Arthropoda. 

 a. Insecta. 



Fertilisation in Nematus ribesii.* — L. Doncaster has studied the 

 gametogenesis and fertilisation of this sawfij. True fertilisation (con- 

 jugation of male and female pronuclei) may occur, and the behaviour of 

 the polar nuclei is slightly different in fertilised and virgin eggs. In 

 the spermatogenesis there are eight chromosomes in spermatogonial 

 divisions ; four " gemini " appear at the beginning of the maiotic phase, 

 and by heterotype and homotype mitoses distribute four chromosomes to 

 each spermatid. In the oogenesis eight chromosomes appear in oogonial 

 mitoses, but in divisions of nuclei in the ovary sheath more than eight 

 are found, suggesting that the chromosomes of the germ-cells are com- 

 pound. 



In the polar mitoses of the agg two types of maturation are found. 

 In some eggs there are successive equation divisions, so that the egg 

 nucleus and each of the three polar nuclei contains eight chromosomes. 

 In other eggs normal reduction takes place, separating entire chromo- 

 somes from one another, and only four are found in each of the 

 daughter nuclei. It is probable that only such reduced eggs are capable 

 of fertilisation, but when unfertilised they may continue to develop at 

 least as far as the blastoderm stage. 



•»^ 



Effect of Heat on Insect larvaB.f — J. Dewitz has experimented 

 with lepidopterons and dipterous larva, and finds that the effect of heat- 

 ing is markedly injurious. Fairly low temperatures, e.g. 40° C, are 

 sufficient in fifteen minutes to induce alterations in the organism 

 manifested by changes in the colour of the blood. Even when exposed 

 to such a temperature for forty minutes, the insect larvas may recover, 

 but their subsequent fate is somewhat uncertain. Since, in consequence 

 of local conditions, larvae are liable to warmth changes in summer 

 analogous to those of the experiments, heat influence is to be regarded 

 as underlying manifold modifications (" Abanderungen "). 



Histolysis without Phagocytosis. | — Charles Janet recalls our 

 attention to the musculature of flight in the queen ants — the biggest 

 thing in the body — which functions only once in a lifetime of perhaps 

 ten years. After the nuptial flight it disappears completely, and is 

 replaced by little columns of adipocytes. A careful study of this 

 degeneration in the queen of Lasius niger shows that the histolysis is 

 accomplished without any intervention of phagocytes. Apparent 

 leucocytes, which have begun in various parts of the body and at 

 various stages to be transformed into adipocytes with albuminoid 

 globules, have been mistaken in insects for phagocytes. The material 



to 



of the muscle ffoes to enrich the blood. 



b 



* Quart. Journ. Micr. Sci. li. (1907) pp. 101-13 (1 pi.). 



t Ceutralbl. Bakt. Parasitenk., 2te Abt., xvii. Nos. 1-2 (1906) pp. 40-53. 



X Comptes Reudus. cxliv. (1907) pp. 393-6 (4 figs.). 



