Terminology: The term'conceptus' is usually defined as the products of a fertilized egg or an
hnplanted blastocyst in a mammal. There is no single terra which applies well to all tissues
derived from a fertilized egg regardless of the egg's phylogeny. Since it will be necessary to
refer collectively to these tissues, however, we use eoneeptus in the broadest possible
sense to include derivatives of the zygote of any species.'Early conceptus' refers here to
products of the fertilized egg prior to formation of a functioning placenta in vivipara and to …