MATURATION OF PARTHENOGENETIC EGGS 



20^ 



same fact in the butterfly Liparis ('89) —a fact which seemed to con- 

 tradict Boveri's hypothesis. Brauer's beautiful researches resolved 

 the contradiction by showing that there are tivo types oi partJienogcne- 

 sis which may occur in the same animal. In the one case Boveri's 









O^cP 



u^ 



D 



^Moo 



'UO' 



V.H>^ 



€r 



(yoo^om 



B 



:■■'■■ '^'^. 



E 



X' -'-'<^2- 



Fig. 100. — First type of maturation in the parthenogenetic egg of Artemia. [Brauer.] 

 A. The first polar spindle; the equatorial plate contains 84 tetrads. B. C. Formation of the 

 first polar body; 84 dyads remain in the egg and these give rise to the egg-nucleus, shown in D. 

 F. Appearance of the egg-centrosome and aster. E. G. Division of the aster and formation 

 of the cleavage-figure; the equatorial plate consists of 84 apparently single but in reality bivalent 

 chromosomes. 



conception is exactly realized, while the other is easily brought into 

 relation with it. 



{a) In both modes typical tetrads are formed in the germ-nucleus 

 to the number of eighty-four. In the first and more frequent case 

 (Fig. too) but one polar body is formed, which removes eighty-four 

 dyads, leaving eighty-four in the o.^^. There may be an abortive 

 attempt to form a second polar spindle, but no division results, and 



