450 



University of California Publications in Zoology [Vol. 22 



a week. Then it was removed, and a fresh bit added. There was a 

 fair growth of the diatom of the genus Navicula throughout the 

 experiment, as well as of small Protozoa, in the aquaria. 



Food. — Several specimens of Oithona nana collected at 8 a.m. 

 showed yellowish brown organic debris, similar in color to kelp, in 

 the stomach. A few pieces of the diatom Thallasiothrix were found. 

 In two cases bits of copepod nauplii were recognizable. 



In the laboratory, adult specimens ate freely of the small bits of 

 fresh and decaying kelp, and also fed somewhat — though far less than 

 of the kelp, on the diatom Navicula. Nauplii began eating this kelp 

 almost as soon as hatched. 



Summary of Results of Rearing Experiments, Oithona nana, in 60 mm. 

 Stender Dishes, Unfiltered Ocean Water 



Material. — Specimens sorted from the 8 a.m. surface collection at 

 the pier were left in a large finger bowl of ocean water for twenty- 

 four hours. Individuals in good condition were then transferred 

 by means of a capillary pipette to rearing jars that had been pre- 

 viously prepared. 



Each specimen was examined daily in the stender dish under a 

 binocidar microscope, and the results recorded. As soon as hatched, 

 the nauplii were transferred to separate jars. After each molt the 

 cast skin was removed, measured, and put into a vial with corre- 

 sponding number. In this manner a complete record was kept of 

 each specimen. 



Table 1 is a summary of the results of the rearing experiments 

 with Oithona nana, first cycle. 



