150 J. 0. WAKELIN BAREATT AND GEOEGE ARNOLD. 



partly iu order to prepare an isotonic fluid for the blood-cells 

 studied, and partly in order to determine the nature of the 

 medium in which the}' lived, to examine the fluid part of the 

 blood also. 



The literature of the subject is scattered and appears to be 

 very scanty, so that further research in the light of the 

 more recent development of methods of investigation seemed 

 very desirable. 



As early as 18(34 Landois (1) studied the blood of insects, 

 noting the colour, smell, and reaction, and ascertaining the 

 presence of iron in tlie serum. He did not, hovvevei*, give a 

 definite classification of the blood-cells, though he states that 

 division takes place by the nucleus usually splitting into two 

 parts. 



The morphology of the formed elements in Molluscs and 

 Arthropods was further studied by Cattaneo (2, 1889) and 

 Wagner (3, 1890). 



Cuenot (4, 1891) gave a voluminous but not very illu- 

 minating contribution to the literature of the blood of 

 invertebrates. This author observed that the blood of 

 Hydropliilus piceus is at first pale yellow, and when ex- 

 posed to the air becomes altered resembling caramel ; neither 

 uranidin, lutein nor fibrin is present; the albuminoid present, 

 which coagulates at 60°-61°, is called hasmopheine. The blood 

 of Blaps, which is also pale yellow, and on oxidation becomes 

 quickly ochreous yellow, contains an albuminoid which is 

 regarded as identical with hgemopheine. 



An important observation in respect of the Coleoptera was 

 made by Durham (5, 1892), who ascertained that the blood- 

 cells of Dytiscus exhibited phagocytosis, readily ingesting 

 particles of Indian ink. 



Reference may here be made to a much more exhaustive 

 examination of the coclomic fluid of Lumbricus by Lim Boon 

 Keug (6, 1896). This author found that the coelomic fluid 

 had a specific gravity of 1*007 to 1*009, and was of alkaline 

 reaction ; it also contained crystals, pigment and microbes, 

 and lield cells in suspension, some of which exhibited phagocy- 



