880 SUMMARY OF CURRENT RESEARCHES RELATING TO 



ceases to be visible wben the integument is hardened and tbe pupa 

 begins to be formed. In the delicate and perfectly transparent 

 nymphs the pulsations of the dorsal vessel in the abdomen are very 

 apparent. Later on the beatings of the heart cease completely. 

 Again they appear, and as many as 60 per minute may be seen ; the 

 movements are now regularly performed till the appearance of the 

 imago. It is clear then that the heart continues to beat during 

 histolysis, and even when the phenomena of histogenesis begin to be 

 apparent. The short period of cardiac arrest corresponds to the 

 moment when the organ undergoes the histological modifications 

 which are specially manifested by the formation of an aortic region. 



Trachese of Insects.* — G. Macloskie, as the result of his re- 

 searches on the tracheal organs of insects, finds that their spiral 

 filaments are not independent structures, but crenulations or inward 

 foldings, with thickening of the chitinous wall ; that the spirals are 

 really tubular, fissured at the line of infolding, and continuous with 

 the inclosing wall. The function of aeration is discharged by air 

 passing, not through the wall into the blood, but directly to the 

 tissues by lung-like terminal cells, described by Louis Agassiz, and 

 shown by Mas Schultze to be especially abundant near the luminous 

 organs of the glow-worm. 



Light of Pyrophorus.f — MM. Aubert and E. Dubois have ex- 

 amined the light of the Elaterid genus PyropJiorus, and find that the 

 spectrum is very fine and continuous, having neither bright nor dark 

 bands ; it extends from between the lines A and B to a little beyond 

 F in the solar spectrum. When the brightness of the light diminishes 

 the red and orange disappear completely; the most persistent rays 

 are the green. When the brightness increases the order of appearance 

 is reversed, the least refractive rays being, in other words, the last to 

 appear. The nearest approach to this phenomenon is to be seen in 

 phosphorescent sulphate of strontium. When the light begins to 

 appear the central and internal regions of the organ are alone 

 luminous ; it is only when the light is very bright that it appears 

 from the peripheral portion, and it is then only that the red rays are 

 seen. The light has an action on sensitized paper, when about 

 2 centimetres from it ; the chemical action is, proportionately, very 

 intense; sulphate of calcium exposed to the light for five minutes 

 becomes feebly phosphorescent, but no results were obtained with 

 sulphate of quinine or a solution of chlorophyll in ether. 



Sting of Mellifera.t— G. Carlet finds that the poison-vesicle of 

 the Mellifera has not the muscular investment which is always found 

 in the Diploptera, that it is not contractile, and it cannot in any 

 way act on its contents. The stylets of the sting have an organ at 

 their base, which may be called the piston, and which appears to be 

 peculiar to this group ; it has a true piston action. The two stylets 

 of the sting may move simultaneously or alternately ; but, in either 



* Amer. Natural., xviii. (1884) pp. 567-73 (4 figs,), 

 t Comptes Kendus, xcix. (1884) pp. 477-9. 

 t Ibid., p. 206. 



