116 Retrospective Criticism. 



by the fishermen of the Adriatic, from the tradition of its being the fish of 

 St. Peter. It seems to me that the corruption of the above term is Hkely 

 to have caused its present appelhition of Jean Dord or John Dory. I am. 

 Sir, &c. — S. Bowdich, Jan. 1829. 



The A'nodon ruglmis of Swainson (Vol. I. p. 96.) is the Anodonta mar- 

 ginata of Say. The latter described a specimen not full-grown, while 

 Swainson's was an old one. You will remember Swainson expresses some 

 surprise that it should have escaped Mr. Say's notice ! ! It is by no means 

 uncommon in our rivers. — J. L. Philadelphia, August 16. 1828. 



Mr. Murray's Paper on the Aerial Spider. — Sir, The strong disinclin- 

 ation I feel to enter into discussions of a controversial character would, in 

 all probability, have prevented me from noticing Mr. Murray's remarks 

 upon my paper on the spiders which produce gossamer, had they been made 

 in that spirit of fairness and candour which one gentleman is entitled to 

 expect from another ; the unhandsome manner, however, in which this 

 writer has conducted his attack (for he has endeavoured to misrepresent 

 my views), renders it imperative upon me to offer a few observations in reply. 



After stating that my opinions relative to the ascent of spiders into the 

 atmosphere do not possess much force, Mr. Murray proceeds thus : — "It 

 does not appear that this author had seen an account of my experimental 

 researches on the ascent of the little aeronaut ; otherwise, he might have 

 hesitated in committing himself to the Linnean Society, in the view he has 

 endeavoured to sustain, but which, however, I believe, is not new. 



" M. Gay Lussac having found that soap-bubbles would not ascend in a 

 room, though their ascent is rapid in the open air, unhesitatingly ascribes 

 their ascent to warm currents emanating from the surface of the ground ; 

 rooted in this opinion, Mr. Blackwall concludes that the flight of the spider 

 originates in a similar cause." 



Now, in supposing that I had not seen h^s essay previously to submitting 

 my own to the Linnean Society, Mr. Murray is completely mistaken. The 

 truth is, I had read it with attention ; but the perusal did not convince me 

 that there existed the least necessity for retracting or even modifying a 

 single opinion I have advanced. The term " committing,*' which Mr. Mur- 

 ray has employed in the passage cited above, to say the least of it, is un- 

 courteous towards myself, and disrespectful towards the learned body 

 alluded to, of which he is a member. With regard to the charge of want 

 of originality, and of having bori'owed my ideas from M. Gay Lussac, I may 

 observe, that I was totally unacquainted with the experiments of that dis- 

 tinguished chemist upon soap-bubbles, and his mode of accounting for their 

 ascent in the open air, prior to the publication of Mr. Murray's paper. The 

 principle upon which I explain the ascent of the spiders which produce gos- 

 samer, I am well aware, has long been familiar to men of science. I make no 

 pretensions whatever to the discovery of any new principle ; but if the ap- 

 plication of one already known, to the solution of an interesting and diffi- 

 cult problem in natural history, which, for more than a century, has exer- 

 cised the ingenuity of speculative zoologists, entitle me to the claim of 

 originality, I shall not withdraw it because Mr. Murray is pleased to insi- 

 nuate that my view of the subject does not possess any novelty. 



In direct opposition to the opinion I ha,ve advanced, Mr. Murray main- 

 tains that spiders have the power of propelling their lines, without any 

 assistance from currents of air. " The aeronautic spider," he asserts, " can 

 propel its threads both horizontally and vertically, and at all relative angles, 

 m motionless air, and in an atmosphere agitated by winds ; nay more, the 

 aerial traveller can even dart its thread, to use a nautical phrase, in the 

 * wind's eye ;' " and, further, he remarks that " these interesting aeronauts 

 sometimes rise with the rapidity of an arrow in the zenith of the observer; 

 at other times, they are seen to float parallel with the plane of the horizon ; 

 andj again, at variously inclined angles. Sometimes the ascent is extremely 



