494 THE AMERICAN NATURALIST. [VOL. XXXIX. 



heterotypic mitosis to his studies on the first division in the 

 tetraspore mother-cell of Dictyota. But it can hardly be said 

 that his account offers any material support to the theory. 

 There is a clear synapsis stage preceding the mitosis in this form 

 from which a spirem emerges as a beaded thread. This spirem 

 then becomes split longitudinally and later the chromosomes are 

 organized and show a longitudinal fission. The form of the 

 chromosomes at metaphase of the first mitosis is heterotypic, a 

 ring form being prevalent, and Williams concludes that it is 

 developed by the bending and closing of the free ends of a 

 loop. The events of synapsis are not clearly enough known to 

 make possible a comparison with the accounts of Allen and 

 Berghs. 



We are now ready to take up the latest conclusions of Stras- 

 burger (:O4b) which are closely associated with views expressed 

 in a recent paper of Lotsy (:O4). Lotsy gives a clear state- 

 ment, illustrated with many diagrams of the various ways in 

 which sporophytic chromosomes may be conceived to unite in 

 pairs previous to the first mitosis in the spore mother-cell and 

 the manner in which the resultant bivalent chromosomes may be 

 divided and distributed by the two mitoses of sporogenesis. 

 Lotsy makes parallel comparisons between sporogenesis in plants 

 and gametogenesis in animals and proposes the term "Gonoto- 

 konten " (" Nachkommenbildner ") for the mother-cells which 

 inaugurate reduction phenomena. The paper presents no new 

 observations but discusses the problems of reduction in their 

 broad aspects. An excellent summary is given by Koenicke 



004). 



Strasburger's (: O4b) most recent paper, " Ueber Reduktionstei- 

 lung," is based chiefly on studies of Galtonia and Tradescantia 

 and presents an entire change of view from his conclusions of 

 1900. Galtonia seems to be a very favorable form for study since 

 the gametophyte number of chromosomes is only six and the 

 structures are exceptionally clearly differentiated in the spore 

 mother-cells, which Strasburger calls " Gonotokonten " after 

 Lotsy. A single spirem is reported to split longitudinally but 

 the two daughter threads remain close together. The spirem 

 then shortens and thickens and becomes distributed in heavy 



