230 First Maturation Spindle of Allolobophora Foetida 



Vierergruppcn entsprechcn. Wie die Abbildung zeigt, kann die Form 

 der einzelnen Griippen etwas variieren, dock muss ausdriicklich bemerkt 

 werden, dass wir JJingbildimgen niemals beobachten konnten. Dagegen 

 sind kreuz- oder x-formige Fignren die haufigsten." 



In Text Figs, -i and 7 they show 37 different forms of the chromosomes 

 of the first maturation spindle of Rliyricliehnis. In our Photo. 72, Plate 

 IV, there is an exact duplicate of one of the chromosomes in their Text 

 Fig. 4, and a comparison of their other figures with our photographs of 

 the first spindle of Allolobophora (Plate IX and our Text Fig. 4 of an 

 earlier paper, '98), show a suggestive similarity in form. Vejdovsky 

 and Mrazek state, and their Text Fig. 5 demonstrates, that only the 

 central part of the first maturation spindle of Ilyodrilus is of nuclear 

 origin, but in Allolohophora a much larger proportion of the spindle is 

 derived from the achromatic nucleoplasm of the germinal vesicle (see 

 Photos. 84 to 89, Plate V). On this point Allolobophora is more in 

 accord with Gathy's, '00, observations on Tubifex, though the membrane 

 of the germinal vesicle persists longer in Tubifex than in Allolobophora. 

 Gathy's Fig. 11 shows the first spindle nearly at the metaphase and yet 

 the membrane of the germinal vesicle is almost intact, whereas in 

 Allolobophora the nuclear membrane entirely disappears before the 

 spindle reaches the metaphase. Our Photos. 84 to 89, Plate V, show 

 part of the membrane of the germinal vesicle persisting until both cen- 

 trioles and asters are present at opposite poles, though not developed to 

 the stage shown in Gathy's Figs. 10 or 11; these photographs indicate, 

 however, that the achromatic nucleoplasm of the germinal vesicle of 

 Allolobophora, like Tubifex, contributes to a large part of the first mat- 

 uration spindle. Allolobophora further supports Gathy's observations as 

 to the independent origin of the two centrioles, their first appearance 

 close to the nuclear membrane and the indication that the spindle is 

 formed under their influence. Gathy omits other important details in 

 the formation of the spindle and his Figs. 8, 9 and 10 demonstrate that 

 he has not observed the successive steps of the development of the chro- 

 matin of the germinal vesicle into the chromosomes. 



Among the Annelids these stages have been most thoroughly investi- 

 gated by Korschelt in Ophryolrocha. '95, and Allolobophora corroborates 

 almost every detail of the process Korschelt describes. In both Oli- 

 goclurtes the chromatin forms a skein, though in Ophrijotrocha the longi- 

 tudinal furrow does not appear until after the chromosomes are formed. 

 The skein divides transversely into chromosomes, in Opliryotroclia these 

 being univalent, whereas in Allolobophora they are bivalent, as a rule 

 remaining bivalent until separated at the anaphase of the first spindle. 



