Spermatogenesis is one of the fundamental but at the same time also one
of the most complex differentiation processes in higher eukaryotes. For
a long time the development of spermatozoa has been considered as
related solely to the needs of transfer of the paternal genome into the
egg. Other paternal contributions to the development of the embryo were
not seriously considered. Only recently has it become evident, from
studies of mouse embryonic development by Solter and colleagues, that
also the paternal genome carries regulatory information into the zygote
since the development of a mouse embryo requires the presence of the
maternal as well as of the paternal pronucleus. This means that we have
to pay more attention to the development of male gametes, since the
imprinting of the paternal genome obviously required for the early
embryonic development must occur during male gamete development. Despite
the fundamental character of sperm development as a cellular
differentiation process, no coherent concepts for studies of this
process exist. Many morphological, and in particular ultrastructural,
details of sperm devel- opment and sperm structure are known, but this
knowledge has not been assembled into a consistent picture reflecting
the basic features of this differ- entiation process. One of the reasons
for the failure to construct such a picture is the fact that also the
genetics of sperm development is poorly developed. For elaborating
concepts of early embryonic development the study of mutants has been,
and still is, indispensible.