46 DUBLIN 



chromosomes in the reduced number appear in Tliysanozooii as 

 nine distinct loops, showing the same polarity and other char- 

 acteristic features described for Pcripatus, BracJiystola, Sagitta 

 and Pedicellina. The bivalents, further, split longitudinally, 

 but at this point, according to Schockaert, the resemblance 

 stops. These chromosomes do not give rise to the structures 

 of the maturation division, but begin to disintegrate and a chro- 

 matin reticulum is formed. After a considerable period of 

 growth, the chromosomes again reform and present themselves 

 as elongated rods, which are more or Jess clearly longitudinally 

 split. The author is not sure of their number, but from the 

 text and figures, it may safely be inferred that they are present 

 not in the normal, but the reduced number. — "En effet, 

 lorsqu'on compte, dans toutes les coupes successives d'un meme 

 ovocyte, les differents tron 90ns persistants du filament nucleinien, 

 on en trouve tantot plus de neuf, tantot moins ; meme en prenant 

 en consideration la multiplication accidentelle de ces trongons 

 par la section du rasoir on constate que leur nombre est tres 

 inconstant." It is at this point that the difficulty arises. The 

 chromosomes now concentrate, removing all signs of the longi- 

 tudinal split, and conjugate two by two along their length. 

 The split between the homogeneous conjugants is therefore not 

 a longitudinal split as nearly all the previous observers (Klinck- 

 owstrom, '97, Francotte, '97, and Van der Stricht, '97) have 

 maintained, but represents, rather, a space between '* portions 

 transversales ... en train de s'accoler." After some slight 

 modifications, these figures present themselves to the spindles 

 in three somewhat different forms : " des anneaux ou des 

 ellipses, des batonnets recombes en crochet a leur extremites et 

 des batonnets longs et droits. Ces trois formes sont dues a 

 I'insertion differente des fibres fusoriales sur les deux branches 

 qui constituent les chromosomes lors de leur genese." These 

 lie with their long axes in the long axis of the spindle and the 

 first division is therefore the reducing division. In the early 

 anaphase, the dyads in the form of U's and rods show again 

 their longitudinal split, which had disappeared early during the 

 concentration period and from this point onward the processes 



