1. Phototactic reactions of young and adult Limulus are described.

2. A method has been developed for studying the optokinetic responses of young animals to moving patterns.

3. Evidence is presented that young animals can see the movement of patterns which consist of light and dark vertical stripes.

4. The response is weak, and visual stimuli appear to have little influence on the behaviour of Limulus. Reasons for this are discussed.

This research was supported by the National Institute of Health, USPH Grant Number NB 03627-03.
 Travel expenses sponsored in part by the European Office of Aerospace Research, Grant AF-EOAR 62-41.