348 SUMMARY OF CURRENT RESEARCHES RELATING TO 



X-rays and Beetles.— Wheeler P. Davey {Joiirn. Exper. Zool, 

 1919, 28, 447-58, 4 fio:8.). In a previous investigation the author 

 shows that X-rays in sufficient amount shortened the life of TriboUum 

 confusum. It is now shown that the life of the beetle may be prolonged 

 by sufficiently small doses of X-rays. The prolongation of life due to 

 a series of small daily doses is greater than that of larger doses given 

 all at once. The lethal efifect of an X-ray dose is less if it is split up 

 into a series of small daily doses than if it is given all at once. By 

 merely varying the size of the dose, the X-rays maybe made to produce 

 at will (1) a stimulation, (2) a destructive effect which occurs only after 

 a latent interval, and (3) an instant destructive effect. J. A. T. 



Behaviour of Tiger-beetle Larva. — Rob. Stager (MT. Naturf. 

 Ges. Bern., 1917, 22-44, 4 figs.). In making its buirow the larvse 

 presses most of the debris into the wall of the shaft. It is in the habit 

 of turning rapid somersaults, jerking itself against the walls. The 

 lower portion of the head forms a rounded polishing instrument. 

 Hooks on a protuberance on the fifth abdominal segment serve for 

 attachment to the wall of the shaft, which may be vertical, oblique, or 

 even in steps. The larva does not leave the burrow. Its head-shield 

 forms a lid to the shaft, and when ants or the like rest on this it is 

 jerked very forcibly against the wall of the shaft near the entrance. 

 The blood of the battered victim is sucked and the husk is thrown out. 



J. A. T. 



Eye-colour in Drosophila melanogaster. — Calvin B. Bridges 

 {Journ..Exper. Zooh, 1919, 28, 337-84). Experiments on "specific 

 modifiers " of eosin eye-colour in this fly. A demonstration is given 

 of eight mutant genes which by themselves produce little or no effect 

 upon the eye-colour of flies homozygous for them, yet which modify the 

 eye-colour in the sex-linked mutant " eosin." These specific modifications 

 are clear and simple cases of multiple genes. Each is the result of the 

 coaction of a specific modifying gene (cream a, cream h, etc.), and of a 

 particular gene (eosin) v^hich serves as a base or chief factor. Each 

 specific modifier is a definite Mendelian gene on the same footing with 

 the whole body of genes known in Drosophila. Each arose by muta- 

 tion, a specific change in the hereditary constitution, by the transforma- 

 tion of the materials of a particular locus into a new form having a 

 different effect upon the developmental process. J. A. T. 



Lecanium persicae and its Symbiotic Yeasts. — G. Teodoro {Redia, 

 1918, 13, 1-5). In this Coccid, as in some others, there is a constant 

 presence of a species of Saccharomyces which lives freely in the hsemo- 

 lymph. A number of units, about a dozen, penetrate the ovum through 

 the nutritive cells. They multiply during development and afterwards 

 become diffused in the embryo. J. A. T. 



Counteracting Insects by Fungi. — Friederichs {MT. Nat. Ges. 

 Bern., 1918, xv-xvi). The susceptibility of injurious insects to parasitic 

 fungi has been utilized with the leaf -bug Blissus hucopterus in Kansas, 

 with Phylloxera in Germany, with sugar-cane Cicadid parasites in 



