14 Dr. \ the Rev. S. (jJialiaiii 13 rail e- 13 irks — 



tliis animal was luminous on stimulation later. The same 

 jjeutleman has since .sent us an example from anotluT 

 Lancashire locality captured on the Dth of August, lUI'J, in 

 the {)arish of Nortlitowu, about two miles from I'adiham and 

 four from Burnley. 



We have not been successful in seeing luminescence in 

 Lancashire or Norfolk under natural conditions. 



Apparalus. 



With living material almost at the very door of our own 

 laijoratory in Darwcn, a problem of first importance was the 

 invention of apparatus for the examination of these animals 

 alive under the microscope. Eventually we hit upon the 

 ])lan of hinging together two sheets of glass each 15 mm. 

 thick, some 81 mm. broad, and some 107 mm. long 

 ( = 3i" X 4^" = photographic quarter-plate), by means of a 

 stout piece of adhesive tape (PI. 1. fig. 7) . Such a glass-holder 

 uill rest splendidly upon any ordinary microscope-stage. 

 To secure a vigorous adult specimen of G. carjiajj/iaiji/s in 

 the holder it is only necessary to open the apparatus to its 

 full extent and allow the animal to walk on one of the 

 sheets and to close the other down upon it gently. The 

 glass is sulKciently heavy to hold such a specimen without 

 injuring it at all, JSmaller specimens need a hohler of 

 smaller dimensions, and with larger species heavier glass 

 could be used with advantage. \t' one wishes to examine 

 the ventral surface of an animal in the holder, since this 

 apparatus is symmetrical above and below, it is easy to turn 

 it upside down and examine under direct light ajjplied by 

 means of a bull's-eye condenser (PI. I. fig. 8). For expcri- 

 inents concerning the secretions of the glaiuls the same holder 

 can be used apart from the microscope, but some form of 

 artificial stimulation is necessary. We have generally found 

 that the current from an induction-coil is the best available. 

 To apply this stimulation electrodes are needed inside the 

 holder in contact witii the aninial's bodv, and for this 

 pur[)ose we have found two strips of tin-foil, a centimetre or 

 more in width and about 10 centimetres long, very con- 

 venient. To apply the electrodes the animal is placed on 

 one side of the open holder, as previously described, and the 

 two electrodes are laid upon its back so that their ends will 

 protrude beyond the closed edges of the sheets of the 

 holder *, the upper sheet of the holder is then gently 



• As ft matter of fact, the electrodes can bo altaclied to the upper 

 plate of the holder, some lime previously, by means of an adhesive, but 



