■420 University of California Publications in Zoology [Vol.22 



relative abundance of the animals, but so far as this summary of 

 results is concerned they have been neglected. It is worth noting that 

 records were taken with the tide-recording machine for long periods 

 during the two years, so that the occurrence of any possible correla- 

 tion between tide and abundance may be investigated, should it seem 

 desirable to do so. 



While the results of this series of plankton hauls are subject to 

 certain sources of error, they are not affected by some other variants 

 which relate to collecting from a boat. Allen (1921, p. 540) has given 

 a list of conditions connected with boat collecting, and they certainly 

 cannot apply to a set of collections made from a pier. The locations 

 at which successive pier hauls were made could not be farther apart 

 than the width of the pier, for in order to keep the net from being 

 caught on the piling it was towed on the side away from the set of 

 the surface drift. The rate at which it was drawn was practically 

 uniform, since there could be no error due to drifting as there is in 

 hauling from a boat. It is assumed, and is a fact which is reasonably 

 certain, that the length of the haul was the same for all the hauls. 



This particular series of collections is of unusual value in the fol- 

 lowing respects. (1) There has never been another series extending 

 over such a long time, in which so many collections were made during 

 each twenty-four hour period. In this particular at least, our series 

 is unique. The work of Herdman and his associates extends through 

 fifteen years, but their 'official' hauls were taken six times a week 

 (Herdman, 1922, p. 141). (2) The collecting was done at a fixed 

 location. (3) Temperature records were made for every haul, and a 

 water sample from which the salinity was determined was taken at 

 each haul. 



My work has dealt only with the Copepoda. which are by far the 

 predominant animals. They are listed under four groups. Two 

 species of the genus Acartia, A. clausi and A. tonsa, were set down 

 in the lists as species. Other small Gymnoplea have been included in a 

 mixed group called "small calanids;" the group includes the genera 

 Clausocalanus, Ctenocalanus, and Paracalanus, and perhaps others 

 closely related to them, but no attempt has yet been made to segregate 

 the genera or species. A second mixed group consists of the Podoplea, 

 comprising such genera as Oncaea, Oithona, MicroseteUa, Conjcaeus, 

 and others. There is no doubt that valuable facts may be obtained 

 from a study of the occurrence of the genera and species of these two 

 mixed groups, and their separation into at least the component 



