MATURATION OF OVUM IN F.CHI NX'S ESCUFFNTUS. 217 



longitudinal cleavages, the secoud split completing itself in 

 the anaphase preparatory to the second division. 



Dixon (1895) gave a somewhat different explanation, 

 involving a longitudinal split taking place for the first time 

 in the metaphase. 



Miss Sargant (1895) described two longitudinal splits in 

 the primary chromatin thread, but adopted an idea of the 

 heterotype, which was essentially similar to that of Farmer's 

 second interpretation. 



Ishikawa (1897) in Allium, and Calkins (1897) in Pteris, 

 described for the first time tetrads in plants. According to 

 the description of the former observer, these tetrads were 

 resolved in the heterotypical division in such a fashion that 

 when the daughter chromosomes broke at their apex a trans- 

 verse cleavage was completed. 



Strasburger and Mottier (1897), under the influence of the 

 idea of the bending of the ring and its subsequent resolution 

 along the same plane, admitted the possibility that the 

 separation of the V figures occurring in the prophases of the 

 second division was a transverse splitting, but a few months 

 later these authors thought they had discovered a longitudinal 

 division during the prophase of the second division. 



Belajeff (1898) pronounced for a transverse division in 

 Weissmann's sense, but Guignard (1899), for Najas major, 

 returned to the interpretation proposed by Strasburger in 

 1895 for the lilies. 



Gregoire (1899) made a re-examination of the phenomena 

 in the Liliaceae, and concluded for a double longitudinal 

 cleavage, the daughter V's in the first division being sepai-ated 

 without further cleavage in the second. 



The difficult point in the heterotype in higher plants a 



single longitudinal split being admitted in the prophases — is 

 to account for the V-shaped forms and their varieties. 

 Strasburger, after changing his ground several times, returns 

 in his last pronouncement (1900) to his ideas of 1895 with 

 some modifications. He finds, as I have already said, the V 

 figures arise in two ways, according to the position assumed 



