ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 579 



action reaches its maximum. The posterior extremity of the dorsal 

 blood-vessel (in D. marginalis and D. jmnctulatus at least) has a slightly 

 elongated form, and terminates in two hps, which function as a double 

 valve. At each systole the lips open under the pressure of the blood, 

 which then escapes ; at each diastole they close again passively and the 

 blood cannot enter. 'In regard to the role of the aliform muscles the 

 investigator agrees with Popovici that they simply maintain the sub- 

 cardiac diaphragm at a certain degree of tension, but that they do not, 

 as is commonly supposed, actually produce the diastole by contracting 

 the lateral walls of the dorsal blood-vessel. The transverse currents 

 found by Newport and Blanchard were made out. They occupy free 

 spaces among the organs and are produced by the inhalent pulsations of 

 the dorsal vessel, and directed towards the ostia by which they can 

 penetrate into it. The dorsal blood-vessel then is not merely an organ 

 of propulsion but functions also, and probably more strongly, as an 

 inhalent pump, and the centripetal circulation of the blood in the body 

 results from the fact that the dorsal blood-vessel tends to draw to itself 

 the fluid in the abdominal cavity. 



Minute Changes in Metamorphosis.* — E. Bordage finds that in 

 many metabolic insects of diverse orders the larval tissues become in 

 great part reserve tissues, with fats and albuminoids. Ferments are 

 probably at work, coming from the fatty bodies or from the imaginal 

 disks. Syncytial masses appear or separate trophocytes. Some of the 

 material is used up ; some passes into the imago. Besides the trans- 

 formation of tissue, there is sometimes a simpler histolysis. Phagocytosis 

 occurs in Muscidae, but not in other cases until after the formation of 

 the pupa. Its importance has been much exaggerated. 



In the metamorphosis of CalUphora, a longitudinal section of the 

 larva, when it is about to become quiescent, shows that the fatty body 

 is represented by two long narrow bands. But the pupa contains an 

 enormous number of trophocytes. Yet it is recognized that the adipose 

 cells of Muscidae do not divide. Therefore the crowds of trophocytes 

 which have made their appearance must be due to a transformation of 

 other larval tissues. It was this observation that led Bordage to a 

 recognition of a general occurrence of cellular transformation in 

 metamorphosis. 



French Mosquitoes and Paludism.-f— E. Eoubaud has experimented 

 in order to find out whether mosquitoes in the Paris region are refractory 

 to the malaria organism. He worked with Plasmodium vivax Gr. and 

 Pel. (var. tertiana Lav.) and PI. prsecox Gr. and Pel. (var. parva Lav.), 

 and found that Parisian specimens of Anopheles mamlipennis are quite 

 able to transmit the disease, and do not form a refractory race. Pre- 

 cautions should be taken. In an appended note A. Laveran emphasizes 

 the reality of the danger in view of the number of soldiers in the 

 country who have been infected with malaria, and indicates that 

 practical measures to prevent diffusion have been in operation. 



* Comptes Bendus, clxv. (1917) pp. 477-9. 

 t Comptes Rendus, clxv. (1917) pp. 401-4. 



