S40 Mr. Earnshaw in Reply to Prof. Kelland on the 



cundation thus consists in the imbibed seminal fluid stimulating 

 the germinal spot to the cell-formation, according to the type 

 of cells in cells. But many more cells are formed than re- 

 main ; the outer layers being constantly absorbed. 



7. The furrows known to be presented by the yelk arise from 

 the formation of cells (see Repertorium, v. 306). Their pre- 

 sence in Fishes was etablished by Rusconi, in Mammals by 

 Barry. In Birds they may either entirely fail, or, as is more 

 probable, be limited to the germinal membrane and not ex- 

 tended to the yelk. 



8. The rotation of the yelk or of the embryo in the ovum, pre- 

 viously observed in invertebrated animals and in Batrachian 

 Reptiles, is also found to take place in Fishes and Mammalia. 

 Rusconi perceived this rotation thirty hours after fecundation 

 in ova of the Pike ; so that it is thus] met with where there 

 is a circumscribed germinal membrane. In the Rabbit it was 

 seen by Barry, although he remained in doubt as to the na- 

 ture of the rotating body which was determined by Bischoff. 

 The latter described also vibrating cilia on the superficial 

 cells. It now remains a point of especial interest, to extend 

 the observation to classes which otherwise do not exhibit ci- 

 liary motion, for instance the Crustacea. 



9. Of the other structures of the [Graafian] follicle which 

 pass out [of the ovary] along with the ovum, the tunica granulosa 

 and retinaada {discus proligerw) undergo liquefaction ; while 

 within the zona there arise concentric formations of membranes 

 andfuid or semifluid rings. According to Barry, this forma- 

 tion amounts to from four to five membranes. The attenua- 

 tion of the zona above mentioned soon disappears. The chorion 

 is not formed out of the zona, but out of cells, which arise in 

 the tube and are laid down around the metamorphosed struc- 

 tures. 



[Professor Valentin then proceeds to give details of the ob- 

 servations of Dr. Barry, the principal of which are the fore- 

 going nine. These details will be found in the Philosophical 

 Transactions for 1839 and 1840. Abstracts of them have 

 been already furnished by this Journal.] 



LIX. On the Theory of Molecular Action according to New- 

 ton's Law: in reply to Professor Kelland. By S. Earn- 

 shaw, M.A., Cambridge *. 

 TJTAVING been long of opinion that the molecular forces 

 •*■ which regulate the vibratory motions of particles cannot 

 vary according to Newton's law of universal gravitation, it 

 * Communicated by the Author. 



