142 REPORTS ON IX\'F.STIGATI0NS AND PROJECTS. 



Report upon Investigations carried on at the Tortugas Laboratory 

 during ipii, by L. R. Gary, of Princeton University. 



REARING OF ZOANTHELLA. 



Continuing the experiments started during June 1910, I collected a con- 

 siderable number of specimens of Zoanthella, mostly Z. semperi, and at- 

 tempted to rear them to the adult stage. A single specimen became attached 

 to the bottom of the dish in which they were kept, and changed its shape 

 until it had become about one-eighth of its original length and three times its 

 original diameter at the base. The oral end retained practically the same 

 size as when it was in the free-swimming condition, and became very re- 

 tractile. The mouth-opening increased in diameter to about three times its 

 former size. The oral disk became broader and flattened. Around the bor- 

 der of the oral disk, at the point where it joins the column-wall, there was 

 formed a prominent ridge, which rose for a considerable distance above the 

 flat part of the disk. This ridge was nearly continuous, showing no indica- 

 tions of elevations and depressions, which would mark the beginning of the 

 growth of tentacles, except at one point, where the ciliated band had for- 

 merly been situated along the side of the larva. When this specimen had 

 been kept under observation for 10 days from the time of its attachment a 

 piece of the glass dish to which it was attached was cemented to a tile and 

 put out on a shallow reef near Loggerhead Key. 



A number of other larvae, when they had shown no indication of trans- 

 forming after having been kept in aquaria for two weeks, were subjected to 

 experiments in which the amount of light admitted to the jars was controlled. 

 One lot of the larvae was kept in the dark for ^2 hours and then brought back 

 into the full light as before. All of these specimens had, when brought into 

 the light, lost most of their algal cells (Zooxanthellse), which had come out 

 from the body of the larva and settled on the bottom of the dish. Of the 8 

 specimens in this lot, 5 underwent their transformation within 3 days after 

 having been brought back into normal conditions as regards the lighting. 

 The 3 remaining individuals never transformed, but showed a broadening of 

 the oral disk area and an increase in the size of the mouth, while still retain- 

 ing the longitudinal band of cilia in an active condition. 



The specimens which went through an otherwise (apparently) normal 

 transformation were unable to attach themselves. They rested on the bot- 

 tom of the containing vessel, but with one exception remained with the pedal 

 disk uppermost. They were finally inclosed in spirals made from silver wire 

 which would hold them in their normal position. One specimen from this 

 lot, while still within the wire ring, was cemented on a tile and put out in the 

 moat at Fort Jefiferson. The remaining specimens were brought to Prince- 

 ton and are at present in the salt-water tanks of the vivarium. 



Other lots of larvse were kept in jars the sides of which were covered with 

 light-proof paint, while the light admitted through the top or bottom was 

 made to pass through blue glass. None of the specimens thus treated trans- 

 formed. Three specimens, which were left without changing the water for 

 3 days in a dish containing about 300 c.c. of sea-water, underwent a partial 

 transformation, such as has been described for some of the specimens kept 

 in the dark for 3 days. These specimens, together with some others which 

 had been recently taken in the tow, were brought to Princeton for further 

 observation. 



