been analyzed by Barnes and Blackstock (1974). 

 We do not know how long it takes for them to reach 

 the adult stage after metamorphosis. Horn et al. 

 (1970), who collected 150 specimens ofLepas pec- 

 tinata, 2-8 mm long, attached to four lumps of tar 

 found floating on the sea surface, noted that, in the 

 laboratory, these animals increased in length by 

 about 1 mm per week. The larger specimens in our 

 collections (20 mm for Dosima, 15 mm for Lepas) 

 contained mature eggs. We have no information 

 on the numbers of generations in the year; our size 

 distribution data (Figure 2) show no evidence for 

 separate generations (which might have been in- 

 dicated by distinguishable size-class modes). 

 Lepas species are known to be widely distributed 

 from tropical to polar seas. Our specimens proba- 

 bly came from populations floating in the eastern 

 Pacific Ocean, which is the most likely area af- 

 fected by the anomalous meterological conditions 

 occuring during June and July 1974 (J. Namias, 

 pers. commun.). 



Summary 



A total of 1,913 specimens of Lepas (Dosima) 

 fascicularis and 642 specimens of L. (Lepas) 

 paciftca, many still alive, were collected on a 

 1,000-m stretch of beach at La Jolla between 5 and 

 9 July 1974. They were attached to various sub- 

 strates which had enabled them to float at the sea 

 surface before being cast ashore. The predominant 

 substrates were feathers (90 pieces, bearing 657 

 Dosima, 221 Lepas), sea grass leaves (122 pieces: 

 835 Dosima, 75 Lepas), brown algae (39 pieces: 

 200 Dosima, 86 Lepas), and tar (57 pieces: 113 

 Dosima, 209 Lepas). Dosima is the predominant 

 species on most of the substrates whereas tar 

 lumps appeared to be preferentially settled by 

 Lepas. The size distributions (Dosima, 1-22 mm; 

 Lepas, 1-16 mm) provided no indications of gen- 

 erational discontinuities. The beaching of 

 these normally pleustonic animals should be 

 considered in relation to preceding and prevail- 

 ing wind conditions. 



Acknowledgments 



We thank Connie L. Fey for her patient help in 

 sorting and measuring the barnacles, James E. 

 Rupert and James R. Lance for taking the photo- 

 graphs, William A. Newman for specific iden- 

 tification of the barnacles and valuable comments 



on the manuscript, and Jerome Namias for discus- 

 sion of relevent meteorological data. Financial 

 support from the Marine Life Research Group of 

 Scripps Institution of Oceanography and from the 

 Foundation for Ocean Research to Lanna Cheng is 

 also grate fill ly acknowledged. 



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LANNA CHENG 

 RALPH A. LEWIN 



Scripps Institution of Oceanography 

 University of California 

 La Jolla, CA 92093 



217 



