扬子鳄胚胎背部皮肤及鳞甲的发生

本文观察了１６例不同时间的扬子鳄（Ａｌｌｉｇａｔｏｒ ｓｉｎｅｎｓｉｓ）胚胎背部皮肤及鳞甲的形态和组织发生过程，孵化第２０天，来自胚胎中胚层生皮节的间充质细胞开始向有皮下迁移，表皮仅具周皮层与生发层两层细胞，第２８天背部鳞片开始明显，左右鳞片之间出现很浅的鳞间沟，前后鳞片交界处的原始表皮，真皮层开始向外突出形成鳞甲原基，第３４天鳞甲原基突出伸长，第４０天背鳞的纵嵴明显，第３４－５０天中，鳞甲后级基

EMBRYONIC DEVELOPMENT OF THE DORSAL SKIN AND SCUTES OF ALLIGATORS SIENSIS

This paper described the morphogenesis and histogenesis of dorsal skin and scutes based upon 16 embryos of Alligator sinensis.At the 20th day of incubation, mesenchyme from mesedermal dermatome began migrating toward the primitive epidermis which consisted of two layers of cells:periderm and stratum germinativum. At the 28th day of incubation, dorsal scales were all distinct with shallow furrows between the right and left scales and epidermis-dermis projection or anlagen for scutes between fore and hind scales. The projections of anlagen for scutes lengthened at the 34th day of incubation. The longitudinal ridges of dorsal scales were evident at the 40th day of incubation. During the 34-50th day of incubation, the epidermis at the base of hind margin of scutes anlagen invaginated gradually toward the dermis at the base of fore margin, and scutes lengthened horizontally to the hind. The dorsal epidermis had three layers of cells at the 34th day of incubation. Pigmentation started to appear in the cells of periderm at the 40th day of incubation. At the 50th day of incubation, the dorsal epidermis had four layers of cells, and a great deal of pigmentation in the cells of periderm was observed.At the 60th day of incubation, the layers of epidermis were similar to that of adult Alligator,and the periderm had degenerated. The cell morohology of dermis appeared varied to each other at the 34th day of incubation. At the 40th day of incubation. the dermis could be divided into the upper and under layers in which network of collagenous fibers and parallelly lined collagenous fibers formed respectively at the 5oth day of incubation. This paper gave a brief discussion on the characteristics about scutes morphogenesis of Alligator sinensis.