A STUDY OF THE BLOOD OF CERTAIN COLEOPTERA. 149 



A Study of the Blood of certain Coleoptera: 

 Dytiscus marginalis and Hydrophilus 

 piceus. 



By 



J. O. Wnkcliii Bairatt, ll.D., D.Sc, 



and 

 Oeorg"e Arnold, aTI.Sc, 



From the Cancer Research Laboratory (Mrs. Sutton Timmis Memorial), 

 University of Liverpool. 



With Plate 11. 



Synopsis of Contents. 



Introduction .... 



Mode of Collecting Blood 



General Characters of the Blood of Dytiscus and 



philus 

 Characters of the Blood-plasma of Dytiscus 

 Characters of the Blood-plasma of Hydrophilus 

 Characters of the Blood-cells 

 Comparison with Mammalian Blood 

 Literature .... 



Explanation of Plate 



Hydro- 



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Introduction. 

 The present iuvestigatiou had its origiu iu a study of the 

 cell diano-es occurrino; in nialio-nant growths, during the 

 course of which attention was directed towards the presence 

 of wandering cells in such growths. It appeared likely that 

 light would be thrown upon the morphology and life-history 

 of the wandering cells of the higher vertebrates by comparison 

 with the free cells of the blood of various invertebrates. To 

 this end the present investigation, which is confined to 

 Coleoptera, was undertaken. The work, however, extended 

 beyond the limits originally assigned, for it became necessary, 



