Abstract
Double monsters in chick embryos have been studied by many investigators. However, many of them examined chick embryos only in early stages of development. Komai et al. (1938) published a detailed study on classification of double monsters seen in chick embryos examined in later stages. The author of the present paper examined duplicities of chick embryos found in unselected dead-in-shell eggs of some hatchary houses in Nagoya city from 1961 to 1964. External appearances and skeletal changes were both examined employing alizarin red S staining. The author of the present paper found several new types of double monsters and attempted to classify types of duplicities of the chicken based on his observations.
