176 CARNEGIE INSTITUTION OF WASHINGTON. 



average 50 micra in diameter and are very transparent, affording exception- 

 ally favorable material for study while alive. The number of chromosomes 

 is about 20. 



Colonies of Palythoa mammillosa bearing apparently mature eggs were 

 found in abundance, and in a few instances male colonies that were throwing 

 sperm were observed among specimens kept in running-water aquaria. 

 None of the eggs could be made to develop by artificial fertilization, nor 

 could more than one or two atypical mitoses be brought about by using the 

 common methods of artificial parthenogenesis. From observations extend- 

 ing over a period of four years and including the months of January, Maj^, 

 June, July, August, September, and October it appears that there is no 

 definite breeding season for Palythoa, but that the sexual products are thrown 

 in small numbers at any season of the year whenever they are mature. 



Experiments with the Eggs of Toxopneustes, hy A. J. Goldfarh. 



During the summer of 1912, I succeeded in grafting the fertiUzed eggs of 

 Toxopneustes variegatus, by a new method which had several advantages 

 over the methods used by myself and by Driesch and Herbst in previous 

 experiments of this nature. The method consisted essentially in subjecting 

 the fertilized eggs to the action of a solution made of approximately 80 parts 

 of sea-water and 20 parts of an isotonic or slightly hypotonic NaCl solution. 

 Relatively large numbers of the eggs were agglutinated and many subse- 

 quently fused at varying stages in their development, and gave rise to types 

 of fused larvae which will be described in detail in Publication 183 of the 

 Carnegie Institution of Washington. It was my plan to determine whether 

 the eggs of other species of echinoderms could be made to fuse together and 

 whether the same treatment would be efficacious. It was furthermore 

 planned to fuse the eggs of different species together by the same method, 

 so that a graft hybrid might be produced, and the antagonistic reactions 

 of the internal organs of each larva might the more readily be studied. 



Considerable difficulty was experienced in obtaining sexually mature 

 Toxopneustes at the Dry Tortugas. At Boca Grande some were obtained 

 and experimented upon. The resulting fused larvae corroborated the find- 

 ings of the preceding summer and afforded materials for the study of the 

 individual histories of such fusions, particularly of the skeletal changes. 

 No other echinoderms were found near the Tortugas sufficiently ripe to 

 test the possibility of fusing different species. At Boca Grande some eggs 

 of Hipponoe were obtained, artifically fertilized, placed in the NaCl solu- 

 tions and gave rise to agglutinated and fused larvae, of the same general 

 types as those found among the Toxopneustes. Not enough eggs, however, 

 were procured to make the grafting of two species possible. 



The same NaCl method was later used at Woods Hole, with the sea- 

 urchin Arhacia punctulata, and an extraordinarily large number of fused 

 larvae were produced. There can be no doubt that the NaCl method was 

 effective in at least three species of sea-urchin eggs, and it is highly probable, 

 in the light of the recent work of de Haan, that different species of eggs can 

 be made to fuse, and enable the experimenter to observe the interesting 

 internal changes of the developing organs involved in such graft hybrids. 



Summary of Work Done on the Fishes of Tortugas, hy E. W. Gudger, 

 State Normal College, Greensboro, North Carolina. 



During the four weeks spent at Tortugas in 1913 I continued the work on 

 the fish fauna begun in 1912. Among elasmobranchs I collected data on 

 the breeding-habits of the nurse shark, Ginglymostoma cirrotum, spending 



