I70 PHYSIOLOGY OF THE INVERTEBRATA. 



and it had a faintly reddish tinge, but no bands could be 

 seen, nor after treatment with acetic acid, which did not 

 remove the colour. On treatment with ammonium sulphide 

 the blue colour disappeared, and could not be again brought 

 back by shaking with air for some time; the fluid had 

 assumed a bronze colour, and with gaslight a faint violet tint, 

 but no bands were seen." 



The blood of lAmnmihS stagnalis assumed a whitish-blue 

 colour on exposure to air, " gave no bands, nor after treat- 

 ment with ammonia, acetic acid, or ammonium sulphide ; the 

 last discharged the colour completely, which could not be 

 restored on shaking with air." 



The blood of Paludina vivipara "is frequently exuded 

 when the animal is pricked with a needle or otherwise irri- 

 tated, and is of a blue colour. It is quite free from bands. 

 Ammonia slightly diminishes the colour, but does not remove 

 it ; acetic acid does not remove it. With neither reagent nor 

 ammonium sulphide could any distinct bands be obtained." 



The blood of the majority of the MoUusca contains hsemo- 

 cyanin, that of a few contains heemoglobin (e.g., Planorbis), 

 while that of others, according to Krukenberg, is devoid of 

 either of these substances. 



Microspectroscopes. 



As the examination of the colouring matters of the blood 

 necessitates the use of a microspeotroscope, we now proceed 

 to describe two forms of this important instrument of re- 

 ■ search. 



The one used by Mr. E. B. Poulton, P.E.S., in his investi- 

 gations on the blood of the Lepidoptera is illustrated in 

 Fig. 32. This instrument has the slit mechanism between 

 the lenses. The upper achromatic lens is adjustable to the 

 slit; an Amici prism is placed over the eyepiece, and the 

 whole connected with the body by a clamping screw. The 

 mechanism worked by the screw P is for contracting and 

 expanding the slit by the symmetrical movement of both 



