Published online by Cambridge University Press: 31 May 2012
The term “protocephalon” as used by Snodgrass (1938) applies to that portion of the head which lies anterior to the mandibular segment. As defined by him it is composed of the “prostomial acron” and a postantennal segment. The term “acron” has been used in somewhat different senses by different authors and to avoid confusion I have introduced the term “blastocephalon” instead. The blastocephalon may be defined as that portion of the head which includes the labrum, clypeus and occulo-antenna1 region. In the germ band it appears as an expanded anterior region, the cephalic lobes, which forms a sort of early embryonic head, hence the name. The posterior trunk-like region of the germ band may then be called the blastocorm.