MATURATION OV OVUM TN ECHINUS ESrUf-RNTUS. 215 



this point ag-ree. In tlie second polar nietaphase I 

 find donble-rod figures, wlilcli are tlie griinddaughter 

 chromosomes lying side by side — each being bivalent like the 

 daughter chromosome from Avhich it sprung. Haecker, in the 

 second metaphase, finds half the number of elements seen in 

 the anaphase of the first spindle, and he accounts for his 

 pseudo-tetrad figures by su]iposing that the previous anaphase 

 figures become linked together. According to his account, 

 there is no second longitudinal splitting apparent, and there- 

 fore the elements are daughter, not granddaughter chromo- 

 somes joined together. Each of the daughter chromosomes 

 is bivalent, so that when united, a complicated redistribution 

 of the elements is brought about according to the formula — 



It ft 



a, (• a b 



X or X 



b d c d 



I i It 



and separation being effected in the plane of the last trans- 

 verse segmentation of the spireme thread, there is a true 

 reducing division. Haecker suggests several possibilities in 

 explnnation of the figures, that just given being his choice; 

 it does not seem very convincing to me^ and the figures lack 

 the inevitable seqnence which is apparent in Echinus.^ 



Returning to my own results, we can only on theoretical 

 grounds assume that each sphere represents a separate 

 chromosome; but the idea certainly provides a plausible 

 explanation, though, of course, such an interpretation de- 

 prives the process of any significance such as Weissmaun and 



' While tliis paper lias been passiiip^ t.lirniitrh tiie press Lerat lias published 

 ill the ' Anatomischer Aiizei^er' a pieiiniiiiary note on the first maturation 

 division in Cyclops streiiuus. He does not adopt the explanations of 

 Kiickert and Haeeker, but briiij;s the first mitosis into Strasburger's scheme 

 of the lieterotjpical division, in which the longitudinal division of the 

 daughter chromosomes is a fundamental eharaetcr. 



