221 



parts of the animal, you have entirely misunderstood me. What I 

 had done, many years since, in investigating the structure of the 

 Naiades, induced me then to believe — and I have never since changed 

 my opinion — that the best natural arrangement existed in the difference 

 of structure of the oviducts. 



Nothing could give me more pleasure than having co-labourers, 

 able and masterly like yourself, in this most interesting subject. As 

 I have intended, for some years past, to take advantage of my first 

 leisure to publish an extensive monograph of our Naiades, all the light 

 or assistance which I could acquire, from all zoologists, would be 

 most desirable to me, and who, in comparative anatomy, could as 

 well aid in such illustration as yourself, so distinguished in this wide 

 field of research? Be assured that when your memoir on the struc- 

 ture and classification of this interesting group of mollusks shall be 

 published, that I shall consider it as a great advance in this branch 

 of zoology. 



You will see, in what I have said above, that you have misunder- 

 stood me entirely in supposing that i could, for one moment, have the 

 slightest objection to your making any arrangement or system that 

 your great experience and good judgment might dictate. If you will 

 look again at my reclamation, you will see that I simply desired to 

 retain the credit of my published observations, which had been 

 recently stated as new, in the report of the Boston Society of Natural 

 History, inadvertently, I hoped, on your part. I claim nothing more 

 whatever, and trust that you will continue your labours without in- 

 termission, until you shall have accomplished the memoir you are en- 

 gaged in, and which you are so able to complete. 



I repeat that I will read your letter to the American Philosophical 

 Society, and at the same time I will explain what I have said above, 

 expressing a hope that you will soon finish your examinations, and 

 give to science the result. But I am sure, on reflection, you will ex- 

 cuse me from printing and distributing your letter, which relates to 

 points on which we do not differ, scarcely touching the simple fact of 

 the reclamation, which is all I contend for. 



Hoping, my dear sir, that in all this j^ou will concur with me, 

 I am very sincerely and truly yours, 



ISAAC LEA. 

 Prof. L. Agassiz, Cambridge, Mass. 



Pending nominations, Nos. 256 to 262, inclusive, were 

 read. 



