Normal stages of development in the lamprey lampetra reissneri dybowski
Zoological Science 5(1): 109-118
ISSN/ISBN: 0289-0003 Accession: 005996857
A series of normal stages of embryonic development in the lamprey, Lampetra reissneri (Dybowski) is presented. The developmental processes from the ovulated but unfertilized egg to the ammocoete larva just before burrowing are divided into 31 stages using as identifying criteria of the stages the externally visible changes such as the appearance of structural changes, the beginning of movements and the body size. The age is determined in terms of an average time at which the stages occur at a temperature of 15.degree. C. The stages and developmental tempos of Lampetra reissneri are compared with those of Petromyzon marinus reported by Piavis.