Scudder.] 282 [April 27, 



The title of Section VI to be altered so as to read " Of 

 Committees of the Council." 



Section VIII, Article I, to be altered so as to read — 



A meeting shall be held on the first Wednesday in May annually. 

 for the choice of officers and other general purposes. At this meeting 

 an annual report, embodying the several reports of the Committees 

 and Librarian, shall be read by the Custodian; and a report on the 

 state of the funds by the Treasurer, who shall also present an esti- 

 mate of the necessary expenses of the ensuing year. 



Section of Entomology. April 27, 1870. 

 Mr. C. S. Minot in the chair. Eight members present. 

 The following paper was presented: — 



On Asymmetry in the Appendages of Hexapod Insects, 

 especially as illustrated ln the lepidopterous genus 

 Nisoniades. By Samuel H. Scudder and Edward 

 Burgess. 



A conspicuous feature in the structure of the higher animals is 

 their bilateral symmetry — the tendency of the organs and frame 

 work to exact reverse repetition upon either side of a longitudinal 

 axis. 



This bilaterality is also shared to a certain extent by some of the 

 lower animals, and is generally more noticeable in the external con- 

 figuration of the body than in the internal organs ; it is apparent, not 

 only in those portions of the body which are disposed in pairs, but 

 also in the central organs, the opposite sides of which repeat each 

 other inversely. 



In the lower animals the exceptions to the law of bilateral sym- 

 metry are frequent and conspicuous, the shells as well as the bodies 

 of mollusks often affording striking examples. Among the higher 

 animals, at least in the exterior sculpture of the body, cases of abso- 

 lute asymmetry are rare ; the most prominent instance occurs in the 

 mature flounders; others are well known, such as the very unequal 

 development of the tusks of the narwhal, and the two sides of the 



