ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 605 



c. General. 



Mechanism of Nuclear Division and of Fertilization.* — R. Geigel 

 discusses the possiljle mechanism of the " attraction " which the centro- 

 somes seem to have on the chromosomes. He maintains that the 

 mechanical interpretation of karyokinesis, based on an hypothesis of 

 attraction, does not work. He discusses likewise the movement of the 

 spermatozoon to the ovum, and the appearance of a receptive promin- 

 ence. After a criticism of various theories which have been proposed 

 to explain this " attraction from a distance," Geigel feels himself com- 

 pelled to postulate a new kind of vital action from a distance. It is not 

 identifiable with gravitational, electrical, or magnetic attraction, but 

 may be ranked along with them. 



Epithelial Movement.f — Albert Oppel has observed in his trans- 

 plantation experiments an active movement of epithelial cells. They 

 Tnay spread over and cover a small bare patch on an epithelium-covered 

 organ, such as trachea or cornea. Epithelial cells which were high and 

 cylindrical, become low and flat. This is a factor in wound-healing and 

 similar processes. It is not the passive result of pressure, but an 

 expression of the contractility of the protoplasm. The movement may 

 be parallel to the base of the epithelial cell, or perpendicular to it. It 

 is quite different from amoeboid movement, which implies pseudopodia 

 and separate elements, and should be ranked beside it, along with ciliary 

 movement and muscular movement, as a distinct kind of movement. 



Interstitial Testicular Cells and Secondary Sex - characters, f 

 J. des Cilleuls has made some interesting observations on the develop- 

 ment of the testes in cockerels and the associated appearance of the 

 secondary sex- characters. It may be recalled that for three or four 

 weeks after hatching, young chickens do not show any external marks 

 of sex. In sex and colour of comb, in plumage and limbs, pullets and 

 cockerels are alike. Towards the thirtieth day, however, the external 

 differentiation begins to be apparent. " By the forty-fifth day the comb 

 is more pronounced and more vividly coloured in the male ; the pullet 

 has the feathers of the tail much more developed, which differentiates 

 her sharply from the cock. From this time onwards the distinction 

 ])etween the characters of the two sexes is gradually accentuated ; the 

 wattles develop in the male, who begins to crow towards the second 

 month." 



So far familiar ground, and it is also well-known that the removal 

 of the testes prevents the development of the secondary cock-characters. 

 But what des Cilleuls has shown is this, that the appearance of the 

 secondary sex characters in the young cock coincides with the appear- 

 ance of interstitial cells in the testes, that the interstitial cells and the 

 cock-characters increase pari passu, and that the cock-characters are 



* Arch. Mikr. Anat., Ixxx. (1912) pp. 171-88 (7 figs.). 



t Anat. Anzeig., xli. (1912) pp. 398-409. 



X O.R. Soc. Biol. Paris, Ixxiii. (1912) pp. 371-2. 



