160 SCIENCE PROGRESS. 



in the fertilisation of the eggs of Axolotl, while indirectly 

 Hermann (18) and others have arrived at similar conclu- 

 sions by showing the " Mittelstuck " to be a derivative of 

 the Nebenkern in several spermatogenetic series, a structure 

 which there is every reason to believe to be the archoplasmic 

 portion of the attraction-sphere. There can indeed be very 

 little doubt that sometimes at any rate spheres do pass into 

 the ovum from the male as the descendants of pre-existing 

 spheres in the antecedent generations of the spermato- 

 genetic series. Others, however, like van Beneden, still 

 hold that the spheres can be evolved in the egg, without 

 any intervention on the part of the spermatozoon ! and in 

 the case of Ascaris they have not yet been shown to be 

 derived from pre-existing spheres in any way. 



And there is still a third, or intermediate class of 

 observers, who conclude from the types they have exam- 

 ined that the spheres are produced in the first instance 

 from both male and female cells alike, being presumably 

 derived from pre-existing spheres in the spermato- and ovo- 

 genetic series, " tous les astrocentres du descendant, etant 

 derives par divisions successives des astrocentres primi- 

 tifs, se trouvent provenir, par parties egales, du pere et de 

 la mere," says Fol (6), who, in his famous and much-criti- 

 cised " Marche du quadrille," figures an aster and centro- 

 some related to each pro-nucleus in the fertilised eggs of 

 sea-urchins, maintaining that each sphere divides before the 

 formation of the first segmentation spindle, one-half of his 

 '' Spermocentre " uniting with one-half of his " Ovicentre " 

 to form a new attraction-sphere at each end of the first 

 spindle-figure. 



More recent observations, like those of Konklin (20) 

 on the zoological, and Guignard (21) in his notable paper relat- 

 ing to the fertilisation of Lilium Martagon, on the botanical 

 side, have arrived at substantially the same results; although 

 it is possible that the figures supposed to be indicative of 

 fusion in these cases admit of other interpretations. 



A vast importance attaches to the supposed fusion of 

 the spheres, since it not only presupposes persistence in both 

 sexes for these structures but suggests that they may have 



