II 



MEIOSIS 



53 



occur, the homologous chromosomes being supposed to come together for 

 the first time in diakinesis. 



Probably such accounts have been due to failure to realize the com- 

 plete temporary disjunction of the ex-con jugant chromosomes which 

 may take place in the diplotene stage (cf. Lepidosiren). Hence the 



Diagram of the constitution of a pair of homologous chromosomes in Lepidosiren, Ascaris 

 and Oncopeltus. The hyphens represent transverse joints in the chromosomes. 



erroneous assumption is made that if the diploid number of chromosomes 

 is found in diakinesis, no previous syndesis has taken place. The classical 

 description of diakinetic pairing without previous syndesis is that of 

 Korschelt (1895) for Ophryotrocha, but the further researches of A. and 

 K. E. Schreiner (1906 b), and Gregoire and Deton (1906), have disclosed 

 that stages of the usual type indicating parasyndesis precede diakinesis in 

 this animal also. 



