92 Journal of the Mitchell, Society [Septemher 



(3, p. 275) report the presence of distinguishable reproductive organs. 

 However, in no single case has any such parthenogenetically produced 

 animal been brought to sexual maturity. 



It is rather too complacently assumed that the production of such 

 mature animals is merely dependent upon the difficulty of imitating 

 conditions in nature. These remarks are not intended to detract 

 from the real achievement of these experimentalists who have demon- 

 strated various methods of stimulating an egg normally incapable of 

 division into further growth. Undoubtedly much light has been 

 thrown upon the physics and chemistry of cleavage ; nevertheless, the 

 present purpose is to point out clearly that, in so far as is now demon- 

 strated, this, instead of being parthenogenesis in the usual sense, is 

 rather the artificial inauguration of a series of divisions of variable 

 length in cells (eggs) generally incapable of further division, which 

 may result in the production of more or less highly developed mons- 

 ters, but which, as the experiments now being described indicate, are 

 utterly incapable of reaching maturity. 



Padina would seem to be an unusually favorable plant in which 

 to test the potentialities of eggs germinating parthenogenetically, 

 since the three individuals included in the life cycle represent both 

 the haploid and the diploid chromosome numbers, reasoning from the 

 behavior of tetraspores and fertilized eggs, and from analogy with 

 Dictyota. Since it is difficult to see how the diploid chromosome 

 number of the sporophyte is to be secured without fusion with the 

 sperm, it might be supposed that eggs germinating with the haploid 

 number could at least duplicate the gametophyte. The experiments 

 above described have, however, shown this, also, not to be the case. 

 The assertion of parthenogenetic germination in Padina, then, is 

 nothing more nor less than the statement that the eggs are capable of 

 a series of cell divisions. It is a fact that the shells were well cov- 

 ered when planted with eggs in division ranging from 1 or 2 cells 

 to apparently well developed young plants. These had all the 

 appearance of normal sporelings, attaching themselves to the shell, 

 putting out rhizoidal filaments, etc. Nevertheless, somewhere be- 

 tween this time and the collection of the cultures they certainly per- 



