int same_species(Reaction *A, Reaction *B);
void decrement_species_count(Species_list *species);
void increment_species_count(Species_list *species);
void check_species_list(Critter *critter, Population *population);
void init_species_list(Population *population);
void decrement_interactions(Species_list *host, Species_list *para);
void increment_interactions(Species_list *host, Species_list *para);