82 JOAN F. POWELL 



acid was excreted during germination as the calcium salt or chelation com- 

 plex of dipicolinic acid. In our work with endotrophic sporulation no cal- 

 cium was present, of course, during sporogenesis, and this prompted an 

 analysis of endotrophic spores for dipicolinic acid and for calcium. As sus- 

 pected, the calcium content was far less than the molar equivalent of the 

 dipicolinic acid present in those spores. Thus, the bulk of the dipicolinic 

 acid was not present as the calcium salt. Inasmuch as these spores survived 

 pasteurization as readily as spores from a complete growth medium, we can 

 only conclude that resistance is not dependent on all the dipicolinic acid 

 being present as the calcium salt. I think this experiment summarizes the 

 final point I have to make, namely, that our solution to the problem of 

 resistance lies not necessarily on what we may find in the spore, but on 

 what are the minimal prerequisites for the distinctive attributes of a spore 

 and spore resistance. 



