728 SUMMARY OF CURRENT RESEARCHES RELATING TO 



tion and gives rise to a mass of globules, whicli finally give rise to the 

 so-called colonial nervous system. The " enigmatic " ectodermal 

 organs are regarded by the author as temporary parts, which take up 

 a dorsal position, and gradually disappear. 



Artliropoda. 



a. Insecta. 



Blood of Insects.* — After alluding to the functions performed by 

 hgemoglobin in the blood of Vertebrates and many Annelides, by chlo- 

 rocruorin in that of other Annelides, and by haemocyanin in that of 

 many Molluscs and the Crustacea, M. L. Fredericq gives an account 

 of some experiments on the larva of Oryctes nasicornis, undertaken 

 with the view of ascertaining whether the same alternating pheno- 

 mena of combination and dissociation, of coloration and decoloration 

 of the blood existed in the case of insects. 



A small incision was made with a pair of fine scissors through the 

 skin of the back and the walls of the dorsal vessel, into which was 

 inserted with care a slender glass cannula. The blood immediately rose 

 in the tube. It is a colourless fluid, presenting nearly the aspect of 

 mammalian lymph, holding in suspension a large number of colourless 

 globules which slightly affected its transparency. It immediately 

 collects in lumps and coagulates spontaneously This coagulation is 

 not stopped by the addition of NaCl., MgS04, &c, ; but a slight rise in 

 temperature (not reaching 55°) is sufficient to prevent it. 



When exposed to the air this colourless fluid soon becomes of a dark 

 brown colour, especially well defined around the masses of globules. 

 Light plays no part in this change of tint, which is due to oxidization. 

 The blood boiled with a little water and completely coagulated still 

 turns brown on exposure to the air ; but that which has been 

 coagulated by alcohol appears to have lost this property. 



The brown fluid, when examined by the spectroscope, shows no 

 characteristic absorption band. At first sight it would appear as if 

 the blood contained a substance similar to haemoglobin or hasmo- 

 cyanin, but this view cannot be supported. 



A clear proof that the coloration plays no part in the respiration 

 of the animal, is, that the brown substance, once formed, constitutes 

 an extremely stable combination which is not decomposed either by 

 acids or by alkalies, and which is not deprived of its colour when 

 placed in vacuo or preserved in a closed vessel. 



The author, therefore, considers that the phenomenon of colora- 

 tion afforded by the blood when exposed to the air is one of death, 

 comparable to spontaneous coagulation. The substance which thus 

 turns brown in air does not serve as a vehicle between the outer 

 air and the tissues that require it. The existence of such an inter- 

 mediary is extremely problematical having regard to the anatomical 

 disposition of the respiratory apparatus of insects where the surround- 

 ing air penetrates by the system of tracheas to the very centre of the 

 living tissues. 



• Bull. Acad. R. Sci. Belg., i. (1881) pp. 487-90. 



