Indigenous Nature q/Pajpilio Podalirius. 643 



Dreissena polymorpha (IX. 573.). — In forwarding to us the 

 drawings for the woodcuts of this shell, Mr. J. Sowerby observes, 

 " I have somewhere published an account of the discovery of the 

 Dreissena in the Commercial Docks ; but I cannot remember 

 where. In that account I mentioned the occurrence of crystals 

 within the shell ; and in the drawing now sent I have intro- 

 duced the crystals. They seldom show more than one face, 

 and only one shell in 500 or 1000 has them at all." False 

 septa are common, resulting, probably, from the superabund- 

 ance of carbonate of lime in the waters of the docks." 



Art. V. Retrospective Criticism. 



INDIGENOUS Nature VapUio Podalirius. — Without ex- 

 pressing any other opinion than that given in my Illustrations 

 (vol. i. Haustellata, p. 8.), as to the indigenous nature of Pa- 

 pilio Podalirius, I cannot refrain from noticing the remarks of 

 Mr. Dale on the subject, contained in p. 599. of your present 

 "Volume ; " truth alone" and not mere opposition, being my 

 object. This writer, in the page above quoted, states, " At 

 p. 333. Vol. III. I gave the different authorities for con- 

 sidering Papilio Podalirius as British. Mr. Stephens chose 

 to consider this * absurd;' giving as a reason, that ' it was a 

 geographical impossibility ; ' and he has been followed," &c. 

 Upon referring to the volume of my Illustrations in which 

 this subject is mentioned, it will be found that I say, " This 

 insect appears to have been introduced into the British 

 fauna upon the most loose and unsatisfactory authority. Its 

 introduction by modern authors arose from the following 

 words of the celebrated Ray : — ' Prope Libernam portum 

 in Etruria, invenimus ; et etiam, ni male memini, in Anglia.' 

 (Ray, Ins., p. 111.); and from the expression of Berken- 

 hout, who says, in his Outlines, that it is 'rare in woods.' 

 Now, as the attention of entomologists has been so especially 

 drawn towards the solution of this point for at least forty 

 years, and no authentic instance of its capture is recorded, it 

 seems absurd to consider it as a British species : but, notwith- 

 standing, there are several entomologists sanguine enough to 

 expect that it may eventually occur in some of the unex- 

 plored parts of the country, although its highest northern 

 range on the Continent appears to be about the latitude of 

 Paris." These remarks of mine were published on June 1. 

 1827; and some additional ones, on June 30. 1828. Mr. 

 Dale's notes (which he now states that I chose to follow) were 

 written on January 3. 1830, and published on July 1. in the 



