ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 945 



j8. Myriopoda. 



Phosphorescence in Myriopoda. — M. J. Gazagnaire,* in face of the 

 discussion between Professors Dubois and Mace on phosphorescence in 

 Myriopods, relates some observations which he has made himself. He 

 found that, in Oryx harbarica, the whole of the ventral surface of the 

 body was luminous ; pressure alone was suflScient to give rise to the 

 luminosity ; it was either total or localized in one or more rings. The 

 light is seen on the sternal plates, and on the anterior and posterior 

 plates of the episternum ; with the aid of a good hand-glass it is possible 

 to detect the presence of a number of cutaneous pores on these plates. 

 On contact these pores secrete a yellowish viscous substance of a peculiar 

 odour ; in contact with air it dries rapidly ; it is insoluble in alcohol, and 

 of an acid reaction. This substance is very phosphorescent, and the 

 light which it emits is intense, persistent, and bluish-green. Owing to 

 its viscosity it attaches itself to objects in contact with it, and makes 

 them luminous for- a short time. In fact, this photogenic material 

 behaves like the phosj)horus of a match on moist fingers. The author 

 thinks that we have here to do with a cutaneous secretion which contains 

 the photogenic matter, and he believes that in other species the facts are 

 the same, and that the photogenic body is always secreted by glandular 

 organs ventral in position. 



M. E. Blanchard f states that he collected a specimen of this luminous 

 Myriopod ; he found the phosphorescent matter attach itself to his 

 fingers, and there show brightly for four or five minutes. He rubbed 

 his fingers on his clothes, and he found that the rubbed parts also became 

 luminous, and presented luminous waves absolutely identical with those 

 of match-phosphorus ; they disaj)peared gradually. It seems to him 

 evident that the luminous substance is distributed over the whole length 

 of the body, or at least over its greater part, and that it is a lic[uid or 

 mucilaginous substance which is easily spread by rubbing. 



S. Araclmida. 



Eelations of Structure and Function to Colour Changes in 

 Spider s.| — The Eev. H, C. M'Cook has some suggestive notes on the 

 relations of structure and function to colour changes in spiders. He 

 points out that as young spiders advance in age their colour deepens ; 

 this must be explained by gradual hardening of the tissues making them 

 more opaque, since, up to this period, no food has been taken. It is not 

 until sedentary spiderlings have established themselves upon their own 

 webs that the characteristic colours of the species begin to appear with 

 any positive degree of distinctness. Moulting seems to produce chano-es 

 in colour-patterns of a very decided kind in some species ; some organic 

 change is probably the cause of this phenomenon. Advanced age, as a 

 rule, makes the colours darker. In gravid females the changes of colour 

 are often very decided; the lighter coloration is probably due to the 

 skin being disturbed and more transparent. The action of the muscles 

 on the skin and chitinous shell or walls, serves to compel certain 

 aggregations of pigment along the lines of use. 



With regard to the relation of environment and habit to colour 



* Bull. Soc. Zool. France, xiii. (1888) pp. 182-6. 



t Tom. clt., p. 186. X Proc, Acad. Sci. Philacl., 1888, pp. 172-6. 



