78 



Mr. L. Hogben. 



not therefore more reasonable to accept as a provisional hypothesis the 

 view that yolk formation is a very intricate interaction of the metabolic 

 functions of plasmosome, mitochondria and Golgi apparatus, a hypothesis 

 which, while unifying the data, is perfectly compatible with the observed 

 transformation of deutosomes (nuclear emissions), chondriosomes and 

 dictyosomes in individual cases ? It is in no way implied that Schaxel's 

 account of nuclear emission in the vitellogenesis of hydroids is accepted 

 for a criticism of this work, Beckwith's paper (20) may be consulted. 



Syiwpsis. 



(1) Nuclear organisation in the germ cells of L. depressa has been- 

 investigated ; emphasis is laid especially on two points : (a) the importance 

 of the study of premeiotic kinetic phases to the interpretation of synapsis ; 

 (b) the independence of the plasmosome as a nuclear constituent from the 

 chromatinic organisation. 



(2) The diploid complex in the male germ cells of Z. depressa consists 

 of twenty-three approximately equal chromosomes, that of the female 

 consisting of twenty-four. 



(3) The chromosomes of the premeiotic mitoses become more curved and 

 display greater individuality inter se as they pass undivided to the poles 

 of the spindle ; in the telophase they spin out into finely granular loops 

 which initially occupy a polar disposition ; they become increasingly 

 attenuated in the spirophase (reticulate stage), so that individually they 

 cannot be identified : in the prophase the reverse process occurs ; they are 

 first recognisable individually as convoluted threads, contracting into beaded 

 loops which become abbreviated to form longitudinally split arc-shaped 

 chromosomes. 



(4) The failure of modern cytological research to confirm the existence 

 of Flemming's continuous spireme makes it imperative for those who 

 advocate telosynapsis in animal forms to postulate some means whereby 

 terminal union of homologous chromosomes can be effected in a manner 

 consonant with the observed data respecting the premeiotic telophase and 

 the synaptic processes. Zoological cytologists who have adopted this view 

 have not yet offered such information. • . 



(5) Parasynapsis can be observed in the oocytes of Libellula : • the method 

 conjunction is probably the same in the male germ cells. 



(6) The transverse axis of the tetrad in the first spermatocyte mitosis 

 corresponds with the longitudinal split in the diplotene stage ; the X-element 

 is segregated in the second reduction division. 



(7) The behaviour of the double nucleolus in Libellula has been investi- 



