142 J. T. CUNNINGHAM. 



au orcliuary resting nucleus. But it may be suggested that 

 possibly the individual chromosomes could be distinguished iu 

 the ordinary resting nucleus, if it was re-examined with suffi- 

 cient care. It may, on further investigation, be found that 

 the fibres of the network of the resting phase are only appa- 

 rently branched and anastomosed, and that it really consists of 

 chromosomes, the limits of which do not entirely disappear. On 

 the other hand, if the network of the germinal vesicle consists 

 of chromosomes, we have to inquire what is the origin of the 

 membrane and nucleoli. The existence of these structures 

 cannot be ignored. The theory that the chromosomes after 

 the last division of a germ-cell place themselves in a convoluted 

 series to form a tangle or spirem, without entirely losing their 

 individual independence, does not account for the appearance 

 of the nucleoli or of the membrane. There are two views of 

 the reconstruction of the resting phase after the mitosis of au 

 ordinary nucleus. According to the most detailed recent 

 descriptions of the process in the blastomeres of a segmenting 

 ovum, the chromosomes become vacuolated, and form little 

 vesicles, which fuse together, and so give rise to the nuclear 

 network, membrane, and nucleolus. According to Flemming's 

 original scheme, the stages of reconstruction were the same as 

 those of division, but occurred in the opposite order : the 

 chromosomes united into a continuous thread, which acquired 

 the intricate convolutions of the tangle-phase or spirem, and 

 then resolved itself into nuclear network, membrane, and 

 nucleoli. According to E-iickert^s views, neither of these modes 

 of reconstruction occurs in the germinal vesicle, the chromo- 

 somes being always distinct. But perhaps while preserving 

 their individual existence these bodies give up and afterwards 

 regain a large portion of their substance, which goes to form 

 the nucleoli. 



Riickert describes the daughter-tangle after the last division 

 of a germ-cell, as consisting of a number of bent chromosomes 

 with their bends all converging towards a " polar region," in which 

 a large nucleolus was often to be seen. He says nothing concern- 

 ing the origin of this nucleolus, but it is certain that the chromo- 



