Pearl, Reactions of Liuuihis. 141 



teacher, I am indebted, not only for the material on which the 

 work was done, which he very kindly furnished me, but also 

 for many helpful suggestions freely offered as the work pro- 

 gressed. When the work on Liinnlus embryos was begun I 

 had already been engaged for two years on a study of the phys- 

 iology of the brain of the adult animal, under his direction. 

 Without the thorough knowledge of the adult behavior thus 

 gained the present study would hardly have been possible. To the 

 authorities of the U. S. Fish Commission, and especially to Dr 

 H. C. BuMPUS, I am indebted for the numerous facilities which 

 were freely placed at my disposal at the Wood's Hole Labora- 

 tory. 



Material and Methods. 



The material used consisted of several hundred developing 

 Linmlus eggs which were given me by Dr. Patten. When re- 

 ceived they were nearly all at about the stage of development, 

 designated as Stage I, by Kingsley ('92). At room tempera- 

 ture development proceeds quite rapidly, but owing to the fact 

 that there is a great deal of variation in the rate of development, in- 

 dividuals in widely different stages of development may be found 

 at any time in the same batch of eggs. The eggs and embryos 

 were kept in shallow glass dishes in sea-water which was changed 

 at intervals, usually once in twenty-four hours. In this way 

 the embryos were kept in good condition for a period of nearly 

 two months. 



The results of the present work will be discussed under 

 two headings : first the behavior and reactions before the em- 

 bryo leaves the ft^^ membrane ("vicarious chorion," Kings- 

 ley's Stage I), and second, the behavior up to the time of the 

 first moult after the animal begins its free existence (the so-called 

 "trilobite" stage, Kingsley's Stage K). General accounts 

 with figures of the morphological development of Limidus are 

 given by Kingsley ('85 and '92). 



The Behavior before the Embryo begins its Free Existence. 



Stage of Development. — The earliest stage at which definite 

 results could be obtained regarding the movements and reac- 



