REDUCTION WITHOUT TETRAD-FORMATION 269 



point of attachment, thus giving rise to -shaped, ^>- -shaped, or 

 XX -shaped figures, all of which in the end assume the -shape. 

 This part of the process is in the main similar to that described by 

 Strasburger and Mottier, and the daughter-V's diverge in the same 

 way as these authors describe. The second division, however, differs 

 radically from their account, since no splitting of the spireme-thread 

 occurs. The chromosomes reappear in the V-, Y-, and X-forms, but are 

 ufidivided, and only half as thick as in the first division. Passing to 

 the equator of the spindle, the V- and Y-forms break apart at the 

 apex, while the X-forms separate into the two branches of the X, the 

 daughter-chromosomes having the form of rods slightly bent at the 

 outer end to form a J-figure (Fig. 135, R-T). This division is, 

 accordingly, a transverse or reducing one, which " corresponds com- 

 pletely to the reduction-division in the animal organism" ('98,2, 

 p. 33.) Atkinson ('99) reaches the same general result in Tnlliuni, 

 stating very positively that no longitudinal division occurs in the 

 second mitosis, and believing that the daughter-V's of the first (hete- 

 rotypical) mitosis retain their individuality throughout the ensuing 

 pause, and break apart at the apex (reducing division) in the second 

 mitosis. This observer finds further that in Arisc^ma the heterotvpi- 

 cal rings of the first mitosis condense into true tetrads, by one longi- 

 tudinal and one transverse division, but believes that in this case it 

 is th.Qjirst division that effects the reduction, as in the insects. 



Such confusion in the results of the most competent observers of 

 reduction in the flowering plants is itself a sufficient commentary on 

 the very great difficulty and uncertainty of the subject; and it would 

 be obviously premature to draw any positive conclusions until further 

 research shall have cleared up the matter.^ 



1 Strasburger's new book, entitled Uber Redtiktionsiheiliing, Spindelbildung, Cfutroso- 

 men nnd Cilienhildner im PJlanzenreich (Jena, 1900), is received while this work is in 

 press, too late for analysis in the text. In this treatise the author gives an exhaustive review 

 of the entire subject, contributing also many new and important observations on Liliuni, 

 Iris, Podophylliwi, Tradescantia, Allium, larix, and several other forms. The general 

 result of these renewed researches leads Strasburger to return, in tlie main, to his conclu- 

 sions of 1895, ^^'ith which agree, as stated above, the results of (luignard and Cregoire; and. 

 in a careful critique of Belajeff's work, he shows how the results of this observer may be 

 reconciled with his own. The essence of Strasburger's interpretation is as follows. In the 

 prophases of the first division the chromosomes first undergo a longitudinal division, shorten 

 to f9rm double rods, and then again split lengthwise in a plane at right angles to the lirst. 

 The following stages vary even in the same species {Uliiini) \ and here lies the explanation 

 of much of the divergence between the accounts of different observers, (i) In the typical 

 case, the chromosomes are placed radially, with one end next the spindle; ami, during the 

 metaphase, they open apart along the first division-jilane, from the spindle outwards, to form 

 h- -shaped figures. These figures meanwhile open apart from the free end inwards along the 

 second division-plane. Thus arise the characteristic o -shaped figures, the daughter-V\s 

 having separated along the first (equatorial) division-plane, while the two hmbs ut each V 

 have resulted, not through bending, but from a secoml (axial) split (I'ig. 135, A-//'). The 



