Miscellaneous. 351 



however, completely in relation to the repeated beatings of the 

 wing-stump against the solid parts surrounding it, or of the corneous 

 pieces which it contains {osselets radicaux of Chabrier), against 

 each other. 



If, in an animal treated as above, the wing-stump is coated with 

 a slightly fluid substance which the air only dries slowly, the pre- 

 ceding sound is sensibly dulled, without the stigmata being in any 

 way modified or the movement of the wings hampered. 



When the section aff'ects the stump itself, the sound produced 

 becomes sharper and weaker. It is destroyed as soon as a sensitive 

 part is reached ; but this, as may be easily ascertained, is because 

 the animal ceases to perform movements which have become pain- 

 ful. 



To sum up, in the Hymenoptera and Diptera the buzzing is 

 due to two distinct causes : — one, the vibrations of which the articu- 

 lation of the wing is the seat and which constitute true buzzing ; 

 the other, the friction of the wings against the air, an effect which 

 more or less modifies the former. It would not be impossible from 

 these data to produce artificially the buzzing of these animals ; and 

 I have some hope of succeeding in this. 



In the Lepidoptera of strong flight, such as the Sphinxes, the 

 soft and full buzzing which those animals produce is only due to 

 the friction of the air by the wings. This sound, which is always 

 grave, is alone produced; it is not accompanied by the basal 

 beatings, owing to a peculiar organization, and especially to the 

 presence of the scales. 



In the Dragonflies also, in which the base of the wings is fur- 

 nished with soft fleshy parts, no true buzzing occurs, but a simple 

 rustling due to the friction of the organs of flight.— Cowip^fs Rendus, 

 September 2, 1878, p. 378. 



Reprodiiction of Hydra. By M. Kokotnefp. 



Notwithstanding its abundance, the freshwater Hydra presents 

 many peculiarities which have been insufficiently studied, especially 

 the rex)roduction of the several elements and the embryonic develop- 

 ment of the individual itself. These phenomena have been described 

 in detail by Kleiuenberg in his monograph on Hydra *. According 

 to his investigation, the cells occur below the ectodermal elements 

 (interstitielles Getvebe), and form an agglomeration serving to pro- 

 duce the ova as well as the spermatozoids. The development of the 

 ovum takes place as follows : — One of the cells of the agglomeration 

 increases remarkably, and swallows up the surrounding cells ; in 

 other words, it feeds upon them. The nucleus is transformed into 

 a germinal vesicle ; and finally the cell itself represents the ovum 



* Hydra, eine anatomisch-entwicklungsgeschichtliche Untersuchung : 

 Leipzig, 1872, with four plates. 



