CELLS IN DIVISION 



Lamp-brush' chromosomes 



In the Amphibian oocyte, the development of the 'lamp-brush' 

 chromosomes begins some time before the deposition of yolk, while the 

 nucleus is already in the diplotene stage of meiosis, in which it remains 

 for the whole of the period of their development (Figure 34). Each 

 chromosome pair then consists of the four normal chromatids with 

 their chiasmata. They begin to elongate and finally attain a length 

 greater even than that of the salivary chromosomes ; at the same time 







wi 



km 



Figure 35 Flemming's drawing of the 

 which the chromosomes are in the 



oocyte nucleus of Ambystoma tigrirmm in 

 lamp-brush stage. From Flemming.^** 



bristle-like lateral branches develop. Thus they assume the appearance 

 which reminded Ruckert^^^ of a lamp-brush, a name which may help 

 a future historian of science to relate the progress of cytology with that 

 of the technology of domestic illumination. In Flemming's ^ellsubstanz, 

 Kern, und ^elltheilung^^* is a drawing of a section through the oocyte 

 nucleus of the Axolotl, in which the chromosomes are at this stage of 

 development (Figure 35). As the bristles grow, they stain less readily 

 and apparently develop into loops, though in electron micrographs the 



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