616 SUMMARY OF CURRENT RESEARCHES RELATING TO 



third case from four ovum-nuclei. If cleavage occurred, the cells would 

 probably have half the normal number of chromosomes in the first case, 

 the normal number in the second, twice the normal number in the third. 

 What occurred, however, was nuclear division without cell division, 

 then a simultaneous division of the egg into small cells, and finally, 

 much the same result whether the egg had given off two polar bodies, 

 or one polar body, or none. The autlior gives a detailed account of the 

 interesting abundance of abnormal mitoses. 



Contraction of Adductors in Fresh-water Mussels.* — W. F. Ewald 

 has made an exact study of the electrical changes associated with the 

 contraction of the adductors in Anodonta and Unio, and distinguishes a 

 " Tonustrom " in addition to the " Ziickungstrom." The tonic muscle- 

 contraction is defined. It is not oscillatory nor discontinuous, but a 

 persistent process, both in its mechanical and electrical aspects. 



Arthropoda. 

 a. Insecta. 



Blood of Insects.f — A. Ch. Hollande has made a comparative study 

 of the blood of insects, partly to see whether there is any marked 

 cytological difference in cases where " auto-hseniorrhage " is usual. He 

 finds that there is no marked peculiarity. But aphides with " cornicles " 

 have free " wax-cells " (cellules cirieres) in the blood which are absent 

 in those without "cornicles." The author describes a variety of leuco- 

 cytes. In most insects there are proleucocytes, phagocytes, granular 

 leucocytes, and cenocytoids. 



Symbiosis of Yeasts and Insects.! — Karel Sulc has studied the 

 so-called " pseudovitellus " and similar tissues in Homoptera, e.g. in the 

 larva of Ptyelus lineatus, and comes to the interesting conclusion that 

 there is symbiosis with various kinds of Saccharomycetes, e.g. Gicado- 

 myces ptyeli lineati g. et sp. n. In another paper§ he deals with the 

 yeasts of Cicadas, e.g. Saccharomyces cicadarum sp. n. 



Migration of Iris-pigment in Compound Eye.|| — R. Demoll has 

 worked specially with Lepidoptera (Agrotis pronuba). A constant 

 tonus from the brain keeps the pigment in its darkness-position. If 

 the tonus be interrupted by narcotics or sleep, the pigment in the 

 proximal part of the iris-pigment-cells takes the light-position. If the 

 tonus is interrupted peripherally by illuminating the proximal part of 

 the iris-pigment-cells between the crystalline cones and the rhabdom, 

 the pigment assumes the light-position. 



Bee Disease.^ — The Board of Agriculture and Fisheries has issued 

 a leaflet dealing with an epidemic disease which has been prevalent for 

 some years past among bees in the Isle of Wight and is now spreading 



* Festschrift R. Hertwig, iii. (1910) pp. 55-66 (5 figs.), 

 t Arch. Zool. Exper., vi. (1911) pp. 283-323 (2 pis. and 12 figs.). 

 : SB. Bohm. Ges. Wiss. (1910) No. 3, pp. 1-39 (18 figs.). 

 § SB. Bohm. Ges. Wiss. (1910) No. 14, pp. 1-6 (4 figs.). 

 | Zool. Jahrb., xxx. (1911) pp. 169-80 (2 figs.). 

 U Board Agric. and Fisheries, Leaflet No. 253 (1911). 



