1918] Essenhcrg: Distribution of the Polynoidae 173 



It has been proved by experimental methods in biological labora- 

 tories that changes in environment, such as slight variation in tem- 

 perature, in chemical composition of water, etc., result in external 

 changes of the animal and often in its death. Loeb (1915), subject- 

 ing Fundulus eggs to low temperature, produced abnormal and blind 

 fish embryos, among which the mortality was very great. The eggs 

 of the same fish when exposed to low temperature for a longer period 

 were killed. Stoekard (1909) treated the eggs of Fundulus with 

 potassium cyanide, and monsters with a single cyclopean eye and 

 with the mouth removed from the extreme anterior tip ventrally were 

 produced. Tower (1906), subjecting the eggs of chrysomelid beetles 

 to different temperatures, obtained beetles of different color. Beetles 

 which developed from the eggs that had been subjected to high tem- 

 perature Avere of dark color, while those that came from the eggs 

 subjected to low temperature (0°-5°C) were of a light color. The 

 mortality of the embryos varied with the period of the exposure to 

 higli or low temperatures and with the age of the eggs and embryos 

 exposed, the more highly developed eggs and older embryos being 

 the more resistant. Many similar cases may be cited which prove 

 that changes in environment, either chemical or physical, have marked 

 effects on animal life. This is especially true of animals in early 

 stages of development. The above mentioned facts suggest the possi- 

 bility that similar environmental conditions may have corresponding 

 effects on the oceanic fauna, and may play an important role in their 

 distribution. 



The aim of this article is to discuss the factors controlling the 

 distribution of the Polynoidae. Conclusions are based on the studies 

 of tlie material in the Zoological Museum of the University of Cali- 

 fornia collected by the U. S. S. "Albatross" and private collectors 

 from the Pacific coast of North America, in addition to a survey of 

 the records of other workers on this subject in this region. 



B. ACKNOWLEDGMENTS 



I take this opportunity to express my sincerest gratitude to Pro- 

 fessor Charles A. Kofoid at whose suggestion this work was begun, 

 through whose assistance I have been able to continue it and whose 

 criticisms have been invaluable. I also wish to express my gratitude 

 to Dr. Olive Swezy for her valuable suggestions and for the interest 

 she has taken in my work. I further wish to express my gratitude to 

 Dr. G. F. McEwen who kindly computed the temperatures for table 5 

 in this article. 



