REPRODUCTIVE CYCLES 637 



by lengthening the exposure of the birds to hght. The Uterature for 

 various invertebrates, along with that for vertebrates and plants, has 

 been recently reviewed (Borthwick et ai, 1956). A search is desirable 

 to learn the extent of photoperiodic regulation of annual gonadal 

 cycles among marine animals which are otherwise subjected to a 

 rather constant environment. 



SUMMARY 



1 . The annual breeding cycles of a number of West Coast echino- 

 derms, mollusks, and crustaceans have been determined, usually by 

 measuring monthly the size of the gonad relative to the size of the 

 animal. 



2. Peaks of gonad size appear in winter, spring, or summer in dif- 

 ferent species, and some breed throughout the year. 



3. Some correlation between fall in temperature and increase in 

 gonad size of the purple sea urchin and the ochre star is observed, but 

 no experiments studying the effects of varied temperature have yet 

 been performed. 



4. The increase in size of the gonad of the ochre star also correlates 

 with the increase in day length; but no experiments on varied photo- 

 periods have yet been performed. 



5. The breeding peak for different years varies by several months 

 for the purple sea urchin; the variability is less for the purple star. 



6. The survey reveals several animals as promising material for 

 experimental testing in the future. 



REFERENCES 



Bennett, J., and A. C. Giese. 1955. The annual reproductive and nutritional 



cycles in two western sea urchins. Biol. Bull, 109, lld-ll. 

 Borthwick, H. A., S. B. Hendricks, and M. W. Parker. 1956. Radiation 



Biology, Vol. 3, Chap. 10. A. Hollaender, Editor. McGraw-Hill, New York. 

 Bullough, W. S. 1951. Vertebrate Sexual Cycles. Methuen, London. 

 Clark, "l. B. 1941. Factors in the lunar cycle which may control reproduction 



in the Atlantic palolo. Biol. Bull., 81, 278 (abstr.). 

 Crisp, D. J. 1957. Effect of low temperatures on the breeding of marine 



animals. Nature, 179, 1138-39. 

 Farmanfarmaian, A., A. C. Giese, R. A. Boolootian, and J. Bennett, 1958. 



