36 SEX IN MICROORGANISMS 



coccoid, refractile, granular forms ranging from 0.2 to 0.5 micron 

 in diameter are suddenly evident at the periphery of the mass. The 

 number of the granular forms increases quite rapidly until a micro- 

 colony is produced (Figs. 22 to 24). In a few instances masses of 

 granular forms appear to extend out from the large body into the 

 medium (Figs. 25 to 27). This process is similar to that described for 

 B. fimdulifoTifiis (Dienes and Smith, 1944) in which the granular 

 forms (so-called Ll forms) grow out from the large body. 



The granular forms of Proteus were not isolated in pure culture 

 by Stempen and Hutchinson. The failure to do this may be due to 

 the peculiarity of the strain employed, because Dienes (1949) and 

 Tulasne (1949b) have reported success. These granules are reportedly 

 capable of reverting to the rod form in subculture. 



The similarity in behavior of large bodies regardless of how they 

 are formed indicates that a basic similarity exists among them. Be- 

 cause large bodies have been reported to occur in old cultures (Hen- 

 rici, 1925) or under the influence of injurious substances such as mer- 

 cury salts, lithium chloride, or penicillin (Dienes, 1946), for instance, 

 these forms have been considered by many to represent dead or 

 dying cells referred to as involution forms. That some of the large 

 bodies observed in cultures are degenerate forms may be true. That 

 this does not apply to all large bodies is shown by two principal 

 points. In P. vulgaris OX- 19, at least, large bodies are often formed 

 early during the growth cycle in a slide culture when conditions are 

 favorable for growth and division of the normal-appearing rods. Also, 

 the large bodies are capable of undergoing further development as 

 indicated above. 



Whether or not large body formation by cell fusion represents 

 a sexual process cannot be stated with certainty. Determination of the 

 behavior of the nuclear material presents the problems outlined above. 

 A genetic approach to this problem is essential. If cell fusion does actu- 

 ally occur only between sister cells, it would be impossible to cross 

 contrasting strains. 



CONJUGATION 



Processes resembling conjugation liave been described for a 

 number of different bacteria. For descriptions of some of the earlier 

 claims, the reader is referred to the review by Lohnis (1921). 



