Cytological Changes Occurring During Germination 



C. F. Robinow 



Department of Bacteriology, University of Western Ontario, London, Canada 



I AM very interested in spores and grateful for the opportunity to attend 

 this meeting but I have not lately worked with spores and have only 

 fragments of fresh cytological studies to offer. 

 One of these, illustrated by Figs. 1-4, concerns the chromatin of B. niega- 

 terium spores. This is one of the few constituents of spores on whose spatial 

 distribution we have fairly reliable information. In B. cereus and B. mega- 

 terium it is arranged in a shape which in optical section gives the impres- 

 sion of a wreath or irregular ring of chromatin encircling the interior of 

 the spore at some little distance inward from the spore membrane. That is 

 how the chromatin is seen alike in sectioned, resting spores ( Robinow, 

 1953), in spores cracked open and rendered stainable by bombardment with 

 ballottini glass beads (Fitz-Jame?, 1953), and in spores fixed during the 

 first few minutes after transfer to fresh nutrient medium ( Robinow, 1953, 

 Figs. 27, 28). What is inside the circle of chromatin? Two different answers 

 suggest themselves of which it is not immediately possible to say which is 

 the right one. 



Is there a relatively large, closed round nucleus in the spore filled with 

 nucleoplasm and chromatin and surrounded by a thin shell of cytoplasm? 

 Or are things the other way around, with the spores filled with cytoplasm 

 in which is embedded, near its periphery, an open net- or basket-work of 

 a few coarse chromatin strands? This ambiguity persists into the early 

 phases of germination. The chromatin is then no longer a mere shell or 

 circle but assumes the shape of variously arranged beaded bars; but, super- 

 ficially, the similarity between the spore interior and an ordinary nucleus 

 is, if anything, greater than it is in the resting stage. This situation is illus- 

 A 



CYTOPLASM 



NUCLEUS 



