Final answer:
The question likely refers to a characteristic the 'primary man M1' has which 'perm M1' lacks, related to a biological difference such as genetic, physiological, or morphological features.
Step-by-step explanation:
The question seems to refer to a comparison between two different forms of an organism, where 'primary man M1' is distinct from 'perm M1.' The blank should be filled with a characteristic or feature that the primary man M1 has, which the perm M1 lacks. Given the context provided, it's not entirely clear what specific feature this might be. However, in the context of Biology, this could refer to a genetic, physiological, or morphological feature that distinguishes two different phenotypes or genotypes of a species.