524 THE AMERICAN NATURALIST [Vol. XL VII 



dition from so slender an evidential basis constitutes 

 a biological comedy of errors scarcely equaled in our 

 literature. 



Cleavage 



Nothing is at present known of the early cleavage 

 stages of the fertilized egg and I shall offer here as a 

 tentative substitute facts dealing with the parthenogenetic 

 cleavage of eggs in atretic follicles. The first step in 

 the development of such eggs is the elimination of the 

 deutoplasmic material, which probably is thrown out of 

 the protoplasm by a rupture of the plasma membrane of 

 the egg. The formative protoplasm of the egg in this 

 way unburdens itself of a considerable volume of inert 

 and probably deleterious material, which, although out- 

 side of the egg-cell proper, remains within the zona pellu- 

 cida and more or less completely surrounds the egg in 

 the form of pseudo-epithelium of cell-like masses, which 

 I have called cytoids. The egg now consists of a homo- 

 geneous, clarified protoplasm and there is every reason 

 to suppose that the elimination of byproducts of metab- 

 olism has served to rejuvenate the cell so that its normal 

 processes of growth and reproduction may be resumed. 

 The nucleus, which, previous to and during maturation, 

 had ceased to carry on metabolic exchanges with the 

 cytoplasm, now evinces renewed activity in that astral 

 rays, entirely absent during maturation divisions, now 

 penetrate the entire cytoplasm and a typical cleavage 

 spindle appears. Two-, four- and eight-cell stages occur 

 in fairly regular fashion, but even at the eight-cell stage 

 unmistakable signs of degenerative changes manifest 

 themselves, which bring about a rapid dissolution of 

 embryonic integrity and inhibit further progressive 

 changes. There is no evidence in this material that 

 parthenogenetic development proceeds to the formation 

 of teratoma or tissue formation; in fact, the total lack of 

 cleavage stages later than about the eight-cell stage 

 argues strongly against the possibility of the develop- 

 ment of any such structures. This study serves two pur- 



