90 EXTERNAL FACTORS III. 2 



the eggs were placed vertically with the blunt pole uppermost, 

 the blastoderm therefore resting against the shell membrane. 



Marcacci has exposed the eggs, inside the incubator, to con- 

 tinual rotation for 48 hours. The eggs were fastened to hori- 

 zontal and vertical wheels rotating 40, 80, and 60 times a minute. 

 At the last mentioned rate of revolution, the direction of rotation 

 was reversed half-way through the experiment. 



Many of the eggs actually hatched out, but the chickens were 

 feeble and liable to disease, and exhibited malformations of the 

 muscles or skeleton. Others, however, died before hatching, in 

 some cases at an early stage, and death seems to have been due 

 to rupture of the vitelline membrane; this was always fatal. 

 The vertical motion was, on the whole, more harmful than the 

 horizontal, owing to the perpetual see-saw. 



It may be noted here that Fere has succeeded in producing 

 retardation and abnormality of development in the Chick by 

 means of short exposures to sound-vibrations. 



Mathews has shown that mechanical agitation violent 

 shaking in a test-tube is sufficient to provoke development 

 (artificial parthenogenesis) of the unfertilized eggs in Asterias, 

 but not in Arbacia (see, however, below, p. 124). 



LITERATURE 



C. DARESTE. Recherches sur la production des monstruosites par les 

 secousses imprimees aux ceufs de poules, Comptes Rendm, xcvi, 1883. 



C. DAEESTE. Sur le role physiologique du retournement des ceufs 

 pendant 1'incubation, Comptes Rendus, c, 1885. 



C. DARESTE. Nouvelles recherches concernant Tinfluence des secousses 

 sur le germe de 1'oeuf de la poule pendant la periode qui separe la ponte 

 de la raise en incubation, Comptes Rendus, ci, 1885. 



C. DARESTE. Note sur 1'evolution de I'embryon de la poule soumis 

 pendant 1'incubation a un ruouvenient de rotation continu, Comptes Rendus, 

 cxv, 1892. 



C. FERE. Note sur les differences des effets des vibrations mecaniques 

 sur revolution de 1'embryon de poulet suivant 1'epoque ou elles agissent, 

 C. R. Soc. Biol. (10) i, 1894. 



C. FERE. Note sur 1'incubation de 1'ceuf de poule dans la position 

 verticale, C. R. Soc. Biol. (10) iv, 1897. 



A. MARCACCI. Influence du niouvement sur le developpement des 

 ceufs de poule, Arch. Ital. Biol. xi, 1888. 



A. P. MATHEWS. Artificial parthenogenesis produced by mechanical 

 agitation, Amer. Journ. Phys. vi, 1901-2. 



