REVIEWS. 391 



produced by the cricket is without doubt produced by friction of 

 the " files " of the two elytra against some other portions of the 

 creature's body, reverberated and enforced by the " drum's " 

 spaces on the two membranous elytra acting as such ; the two 

 lower wings are what are supposed to be the other appliances 

 used, and in the rapid opening and shutting of the elytra, the 

 " files " mounted on them are supposed to be rasped over the 

 ridges rising from the surfaces of the lower wings. I would 

 recommend those who desire to understand the operation 

 thoroughly to read the article referred to. 



There are other explanations offered of the operation of 

 chirping, besides that given above. It appears to be the male 

 insect only that is musical. Hahnemann Epps. 



Elytron of Cricket— Referring to the note by Mr. Epps, and 

 on close examination of the object with a high power, I should 

 suggest that the shrill sound is produced by the vibration of the 

 stiff hairs on the ridges of the elytron ; the hairs catching each 

 other, and on springing back producing the sound, which is 

 increased by the expansion of the sac to tightness, in the same 

 way as a pin stuck firmly into a table or sounding-board gives a 

 loud tone. Imagine a pin securely fixed on the end of a drum, 

 and caused to vibrate, the tone is greatly increased. I should 

 imagine that the wings are raised from this moveable sac (?), and 

 act as a deflecting board, throwing the whole sound in one 

 direction. S. R. Barrett. 



L'Annee Biologique ; Comptes rendus Annuals des Travau 

 de Biologic Generale. Publics sous la direction dc Yves Dclage. Roy. 8vo, 

 pp. xlviii. — 732. (Paris: C. Rcinwald. 1897.) Price 20 francs. 



This is an important Year-Book, compiled by Prof. Delage, and a number 

 of associate editors, giving an analysis of many hundreds of books, magazine 

 articles, etc., relating to biological research. The methodical arrangement of 

 the subjects and the excellent index renders this work an admirable work of 

 reference for all who wish to become acquainted with the newest biological 

 theories. 



The editor. apologises for the delay in publishing this volume, which gives 

 a resume of the work of the year 1895, but the volume for 1896 will very' 

 shortly be published, after which it is believed there will be less delay. 



