LEONARD MUSCATINE 259 



affected weight loss was tentatively ruled out since albinos in light 

 and darkness lost weight at the same rate. We therefore conclude 

 that the lower rate of weight loss by symbiotized anemones is re- 

 lated to the presence of algae. 



These observations, along with evidence from tracer studies (9), 

 suggest that during starvation carbon contributed by the algae, 

 together with host excretory nitrogen, is used for the synthesis of 

 organic compounds necessary for maintenance of weight. This view 

 emphasizes the possible secondary role of the algae in reclaiming 

 waste nitrogen. 



STUDIES ON HYDRA 



With the introduction of techniques for the mass culture of 

 Hydra (7) an opportunity presented itself for quantitative studies 

 on plant-animal symbiosis in the laboratory. Chlorohydm viridis- 

 sima/' a hydra containing zoochlorellae within its gastrodermal cells 

 ( 14 ) , may now be grown under controlled environmental conditions 

 and in a fluid of known ionic constitution. Growth may be measured 

 in terms of protein or logarithmic increase in number of hydranths 

 (6). In addition, problems encountered with sea anemones, such 

 as removal of algae and erratic feeding behavior, are easily 

 resolved. 



C. viridissima was routinely grown in our laboratory in the fol- 

 lowing culture medium ("M" solution): 10 "^M Tris (hydroxy) 

 methylaminomethane buffer, pH 7.6, lO'-^M CaCL, 10 'M 

 NaHCOs, 10-W KCl, and IQ-^M MgCL, in de-ionized water. 



Algae-free C. viridissima were obtained by growing green indi- 

 viduals in M solution plus 0.5% glycerin (v/v) for 7-10 days, 

 following the original technique of Whitney (13). These albinos 

 then grew normally in M solution and did not regain an algal flora. 



Growth studies. All growth experiments were conducted at 

 21°-23° using the method of Loomis (7). Ten hydranths (five uni- 

 form hydra, see ref. 4) from mass cultures were put in 30 ml. 

 of M solution in shallow Petri dishes placed four inches from a 

 single 40-watt fluorescent light ( Sylvania-Cool White). Daily, the 



^Tentative identification. 



