20 SCHMIDT ON THE COMPARATIVE PHYSIOLOGY 



Rhynchota . . Aphis (rosa), Nepa (cinerea), Hydrometra 



[paludum). 

 Antliata . . . Simulia [reptans), Musca {domesHca and vo- 



mitoria), Sargus (cuprarius). 

 Glossata . . . Tinea [pallionella), Hybernia [brumata), Bom- 



byx {pint), Cossus {Jigniperda), Sphinx {li- 



gustri), and some others. 

 In addition to these, many larvae and pupae, partly from those 

 genera and species enumerated above, partly from others, the 

 systematic names of which I did not note at the time and have 

 now forgotten. In all, the minute structure presents great ana- 

 logy in the elegant grouping of the layers of longitudinal and 

 transverse fibres which has been mentioned. On treating them 

 with potash, we find the most amusing metamorphoses ; the most 

 splendid Vanessa Antiopa, Sphinx or Papilio becomes as colour- 

 less and transparent as the commonest bee ; the Swallow-tailed 

 butterfly (P. Machaon) with its most elegant play of colours cannot 

 be distinguished from the common moth. On directing our at- 

 tention to the Crustacea we obtain the same remarkable result. 

 If we extract the lime-salts from the thoracic shield of the Craw- 

 fish with dilute acid and macerate it for a couple of days in hot 

 solution of potash, we obtain a colourless skeleton of chitine, in 

 which, with the aid of the microscope, numerous interwoven 

 layers of longitudinal and transverse fibres may be distinguished. 

 In this case, the lime-salts appear to occupy the place of the 

 resinous colouring matter of the beetles, as a uniting medium. 

 The number of these fibrous layers increases with the age and 

 thickness of the shield, and hence is very considerable in the 

 Lobster. The shield of the craw-fish, lobster and a Squilla 

 (mantis) was prepared in considei'able quantity in the various 

 ways above mentioned ; the basic substance in all, as the follow- 

 ing data will show, is perfectly identical : — 



a. Astacus fluviatilis. Tegument. 

 Determination of the Ash. 

 0"247 substance gave 0*005 ash = 2*0 per cent. 



Nitrogen. 



I. 0'412 substance gave 0*424 ammonio- chloride of platinum 

 = 6*59 per cent, nitrogen. 



II. 0'360 substance gave 0'357 ammonio- chloride of platinum 

 = 6*35 per cent, nitrogen. 



