A dynamic model for cell differentiation is studied, where cells with internal chemical reaction dynamics interact with each other and replicate. It leads to spontaneous differentiation of cells and determination, as is discussed in the isologous diversification. Following features of the differentiation are obtained: (1)Hierarchical differentiation from a “stem ” cell to other cell types, with the emergence of the interactiondependent rules for differentiation; (2)Global stability of an ensemble of cells consisting of several cell types, that is sustained by the emergent, autonomous control on the rate of differentiation; (3)Existence of several cell colonies with different cell-type distributions. The results provide a novel viewpoint on the origin of complex cell society, while relevance to some biological problems, especially to the hemopoietic system, is also discussed. 1

In this paper, we propose an associative memory system based on parametrically coupled chaotic elements. The proposed system is obtained by adding a new parameter control to our previously proposed system. A chaotic activity in an early association stage makes an efficient association over the memories that are stored by means of autocorrelational learning. When the system successfully recalls the target memory, the system's motion is dominated by a spatially coherent oscillation, while unstable motions remain when the system fails to make the association. In addition, the system has a large memory capacity. A comparison between the proposed system and an approach with a nonmonotonic transfer function is also shown. Acknowledgement The authors would like to thank Dr. Masato Okada of Kawato Dynamic Brain Project, Japan Science and Technology Corporation, for his invaluable comments and suggestions. The authours also wish to thank Professor Shuji Yoshizawa of University of Tokyo, for hi...