NUCLEOLI IN PED1CELLINA AMERICANA. 361 



among my Auerbach preparations, and the results dispel any 

 possibility of confusion. The nucleolus, at this point completely 

 vacuolated, stains intensely red and, in most striking contrast, all 

 the chromosomes lying on its side are as intensely green. It is 

 hardly possible that this striking distinction in staining capacity 

 would exist if there were any more intimate connection between 

 the chromatin and the nucleous, than mere apposition. But more 

 conclusive evidence is given by the fact that the characteristic 

 concentration and localization of the chromosomes, immediately 

 before the first maturation division, is, in most instances, passed 

 through without any relation to the nucleolus. In addition, the 

 history of the chromatin in the growing oocyte is of a nature en- 

 tirely incompatable with the conception of the authors cited above. 

 As is pointed out in the section on oogenesis (Dublin, '05), the 

 chromosomes persist, in the reduced number, from the period 

 of synapsis up to the time when they enter into the first matura- 

 tion spindle. At no stage is there a break in this continuous 

 history. At no stage is a chromatin reticulum formed which 

 might, in some way, make the continued observations of the 

 chromosomes an uncertain task. On this point, the evidence 

 appears to be decisive. These indented nucleoli often occur, 

 when the chromosomes are at the highest point of their exten- 

 sion, as threads, and when even the smallest of them would be 

 many times as large as the space out of which they are supposed 

 to arise. We can now understand the true significance of a con- 

 dition such as is shown in Fig. 14, c, where the chromosomes 

 radiate from the nucleolus and seem to originate from it. This 

 is simply a case, rare enough, where the chromosomes in their 

 extension through the nucleus have crossed such a body. It is 

 probable, further, that they have been intimately associated with 

 the nucleolus by the coagulation incident to the fixing process. 

 In connection with the deep staining cap-formation on the 

 much vacuolated nucleolus, it is very probable that we are con- 

 cerned with a phenomena similar in all respects to that observed 

 by Obst, '99, in Liina.r, and in other Molluscs, where a nucleolus 

 was found to arise from the chromatin in the process of concen- 

 tration. These nucleoli arise late in the oocytic growth and, in 

 contrast with the cyanophilous nucleoli of the early oocytes, they 



