158 Lloyd Williams . — Shi dies hi the Dictyotaceae. 
then disappear. The study of these makes it clear that in the karyokinetic 
stage the bulk of the nucleolus is cast out into the cytoplasm in the form 
of fibrillae and globule, and it does not seem that either substance is used 
in the formation of the spindle, for they coexist with the mature spindle 
up to a late stage in metakinesis. The appearance of the new nucleolus 
follows so quickly upon the stage when the nuclear membrane encloses 
nothing but the dispirem, that we are forced to the conclusion that the 
substance separates from the chromosomes. 
The centrosomes and other accessory structures will be discussed when 
the cytology of the sexual generation has been described. 
With regard to the development of the chromosomes it is clear that 
if the description given above be correct, whatever the details of the 
metaphase stage may be, a transverse division of the chromosomes must 
occur somewhere. No other theory seems to account so satisfactorily for 
the facts as that of Farmer and Moore, already referred to ; and I regard 
the figures of the prophase stage in the three Dictyotaceous genera ex- 
amined as strongly confirmatory of the hypothesis. 
