THE GENERAL OUTLINE OF MEIOSIS 67 



ally be no prophase to the second division. In this 

 case the telophase nuclei of the first division will 

 pass directly (by loss of their nuclear membranes) into 

 the prometaphase of tlie second division ; a spindle 

 will develop and wo have reached the metaphase of 

 the second division by a ' short-cut ', involving the 

 entire elimination of a prophase. In any case the 

 prophase of the second division, even if present, is 

 always short. 



The prometaphase of the second division differs 

 from that of an ordinary mitosis in two respects, (1) 

 the number of chromosomes is half the somatic 

 number, (2) the chromatids diverge widely, being 

 only held together at the spindle attachment and 

 not approximated throughout their length as at 

 mitosis ; they tend, however, to come into closer 

 contact at the metaphase of the second division. 

 In some cases the second division chromosomes 

 appear to resemble those of an ordinary mitosis in 

 having only one spiral (and not a ' major ' and a 

 ' minor ' one as at the first meiotic division). 



Anaphase and Telophase of the Second Division 



These do not differ from those of an ordinary 

 mitosis, so that it is not necessary to describe them 

 in detail. Between the spindle attachment and the 

 first point of crossing-over the second anaphase 

 always leads to the separation of maternal from 

 maternal chromatids or of paternal from paternal 

 ones (Fig. 16). 



One last question in connexion with meiosis 

 remains to be considered. If the whole process has 

 arisen by profound modification of two mitoses, and 

 if the chromosome ' split ' of the first one is delayed 

 until pachytene, what has happened to the ' split ' 

 corresponding to the second division ? Usually there 

 is no trace of it but various authors ^^' ^^^ have claimed 

 to have seen a split down the middle of the anaphase 

 chromatids of the first division. Such a split, if 



