DEPARTMENT OE MARINE BIOEOGY. I47 



\ 

 EMBRYOI^OGY OF PALYTHOA. 



Attempts to obtain the embryos of Palythoa mammilosa were continued 

 during the present summer without success. The eggs were still immature 

 when examined on August 7, although the testes were rapidly increasing in 

 size and ripe active spermatozoa could be obtained in abundance. All 

 attempts to induce artificial parthenogenesis resulted only in membrane 

 formation without any subsequent segmentation. 



EMBRYOLOGY OE FISSURELLA. 



Two lots of Fissurella eggs were fertilized and carried through to the 

 formation of free-swimming embryos. Some 50 individuals were collected 

 on July 23, when the low spring tide came on an excessively hot day. None 

 of the eggs from any of these specimens could be fertilized, and all subse- 

 quent attempts to fertilize the eggs of this form failed. As the result of the 

 high temperature on the reef on the above-mentioned date more than 50 per 

 cent of the snails collected at that time died, or were washed out from the 

 shells (they may have been dead when taken into the live-car), during the 

 succeeding night. As the ovaries of the females were full of eggs, which 

 shook out when the ovary was put into a dish of water, it seems that the 

 heat, which was fully 38° C, was sufficient to destroy the eggs without being 

 great enough to kill all the snails. 



The Madreporaria and Marine Bottom Deposits of Southern Florida, by 

 Thomas Wayland Vaughan, U. S. Geological Survey. 



During June 191 1 studies of the life-history, growth-rate, and general 

 ecology of the corals of southern Florida were prosecuted along lines begun 

 in preceding years. Especial attention was paid to rearing coral colonies 

 from planulse that attached themselves in the aquarium and were therefore 

 of definitely known age ; to rearing colonies from planulae that had settled on 

 collectors and were therefore of ages approximately known ; to planting in 

 selected localities colonies cemented to terra-cotta disks (tiles) ; to making 

 measurements of colonies growing naturally in certain localities; and to 

 repeating annual surveys of the piers of the Fort Jefferson wharf and of the 

 Fort Jefferson moat. One result of these experiments and observations was 

 to obtain data on the factors that influence the attachment of planulae, their 

 survival after attachment, and their growth-rate should they survive. Other 

 additional information on the general ecology of these organisms was pro- 

 cured, and new observations and experiments were initiated. A brief account 

 of the investigations on the Madreporaria and a summary of the results 

 obtained follow. 



The effects of the hurricane of October 17, 1910, were studied, and a 

 series of samples of the bottom deposits was collected on the Quicksands 

 lying west of the Marquesas Keys and around the Marquesas. The informa- 

 tion obtained from these sources will later be used in describing the active 

 geologic processes of southern Florida. However, it may here be stated that 

 there is much fine calcareous sediment on the Quicksands, and a deposit of 

 ooze, of an undetermined number of feet in thickness, occurs in Marquesas 

 Lagoon ; this ooze is extremely fine and is probably a chemical precipitate. 

 (For a possible explanation of such a precipitate, see the report of Mr. G. H. 

 Drew, pp. 136-141 of this Year Book.) 



