528 BULLETIN OF THE 



Auerbach, are the facts that the asters have been shown to arise at a dis- 

 tance from the nucleus, and before the latter had suffered recognizable dimi- 

 nution in volume. 



The idea that the asters are the optical expression of currents of clear 

 protoplasm setting toward the " centres," has much more in its favor 

 than the theory of centrifugal currents. It does not conflict with the 

 view, in support of w^hich there is much evidence, that these are centres 

 of attraction, and it is readily harmonized with the fact that there is an 

 accumulation of clear substance — the " areas " — about these centres, 

 which seems to present the same properties as the substance of the rays. 

 It, nevertheless, appears insufficient to explain all the observed phe- 

 nomena. If the star is due solely to centripetal currents, it is unin- 

 telligible how it should attain such a size as it often does without 

 a corresponding accumulation of clear substance at the centre, or why, 

 on the other hand, " les rayons de Taster male ne commencement a se 

 montrer nettement que plusieurs minutes apres la fecondation et lorsque 

 la tache claire s'est dejk avancee un peu vers I'interieur du vitellus." 

 (Fol.) Another obstacle to this view is the deportment of the rays 

 in certain special conditions of the aster. If the spiral course which 

 they sometimes exhibit is induced by any mechanical or other influence 

 after their formation,* it seems impossible to explain them as simply 

 currents of either protoplasm or nuclear fluid, since any extraneous 

 force which could produce such extensive alterations in the direction of 

 the rays would obUterate so susceptible a thing as a stream of fluid. 

 But whatever may be the conclusion respecting the rays of the spiral 

 asters, the lateral deflection of those constituting the peripheral star 

 during the formation of the polar globules is evidently the result of a 

 mechanical influence. They are secondarily altered in direction, but 

 maintain their individuality, notwithstanding the pressure which pre- 

 vents their assuming a rectilinear position. If in this case the rays 

 were onl}'- streams of fluid, the resistance off'ered by the eg^ envelope 

 would merely result in shortening them without causing any such modi- 

 fication of direction as has been repeatedly observed. The astral rays 

 are visible in virtue of their possessing diff'erent refractive power from 

 the intervening portions of the protoplasm, not simply by reason of the 



* If it were assumed, on the other hand, that the spiral condition was not super- 

 induced, but was from the beginning of their formation characteristic of all asters in 

 which it is found, it would be difficult to explain why the currents followed such a 

 systematic and yet indirect course, unless one assumed in addition the pre-existence 

 of a special structural condition of the protoplasm determining the direction of the 

 currents. But there is nothing else to favor this latter assumption. 



