DEPARTMENT OF MARINE BIOLOGY. 125 



the young actinians went beyond this "Edwardsia" stage, although some of 

 them remained alive for more than two weeks. 



In the diatom jars several of the larvae became attached by the oral end, 

 which on the formation of the tentacles became very much broadened. These 

 individuals also remained in the eight-tentacle stage for several weeks ; they 

 were fixed at the time of leaving the laboratory. 



RATE OF GROWTH AND REGENERATION IN ALCYONARIANS. 



Several species of alcyonarians were studied to determine their rates of 

 growth and powers of regeneration under normal conditions. Isolated in- 

 dividuals, that could be identified at any time on the reefs, were chosen, so 

 that all the conditions of their environment would be normal. Measure- 

 ments of many colonies were made, both those with only a few polyps and 

 others at least a year old. The location of all these colonies was charted so 

 that they can be kept under observation during another season. In the 

 regeneration experiments all of the operations were extensive. The colo- 

 nies were charted in the same manner as for the growth records. When 

 last examined, some two weeks after the operations, the amount of separa- 

 tion was unexpectedly large. 



EMBRYOLOGY OP PALYTHOA. 



The eggs of a Zoanthid actinian (Palythoa mammilosa) were obtained 

 in abundance from colonies incrusting the shallow reefs about Tortugas. 

 There were no ripe male colonies to be found, but by chemical means arti- 

 ficial parthenogenesis was brought about. In no case did the segmentation 

 result in the formation of more than an irregular planula. 



Only a small proportion of the eggs obtained could be stimulated to de- 

 velop by chemical means, and these invariably came from colonies that on 

 the reef could be recognized by their dark-brown color. This fact, as well 

 as the absence of ripe spermatozoa, seems to indicate that the breeding- 

 season of Palythoa is later than the first of July. 



EMBRYOLOGY OE FISSURELLA. 



A few ripe individuals of Fissurella were obtained, the eggs artificially 

 fertilized, and carried through until free-swimming embryos were obtained. 

 On centrifuging these eggs a very striking color separation of substances 

 was obtained, but owing to the fact that so few eggs were available this 

 phase of the work was not carried far enough so that no definite results 

 were obtained. 



PEDAL LACERATION IN AIPTASIA. 



Material was collected for the study of the processes of the readjustment 

 of tissues in the formation of small individuals by "pedal laceration" in this 

 species. The young given off in the normal manner were preserved, and 

 also, for comparison, those resulting from cutting off small fragments from 

 the outstretched bases of adult individuals. This material was secured to 

 supplement some already collected at Beaufort, North Carolina, and at the 

 Bermuda Biological Station. 



