242 BULLETIN OF THE BUREAU OF FISHERIES. 



injured tissues. The process goes on usually without interruption till the fission has separated the 

 basal portion completely, the last rupture of the lateral threads occurring with a more or less sudden 

 break and the prompt contraction of the free ends. 



The upward fission is fairly rapid, and soon the oral disk and mouth become involved in the opera- 

 tion. The fission is almost invariably finished upon one side at a time; that is, one half seems to yield 

 more readily than the other, and the rending of the tissues of that side may be complete as much as a 

 half hour before that of the other. Indeed, it would seem as if there was something of arrest in the vigor 

 of the pulling when the fission had completed itself throughout one half. As the process of either side 

 approaches completion the last vestige of the oral disk becomes spun out into a delicate thread 5 or 6 

 mm. or more long, in a tremendous state of tension, the final rupture of which takes place with a more 

 or less sudden rebound of the ends and sides of the body. The final rupture of the other side seems to 

 take place more slowly, but is soon accomplished, when the two halves of the divided actinian assume 

 a more or less erect aspect, fold the edges inward until the opposite edges approximate and finally unite 

 and gradually heal over, each becoming an independent individual. The healing and internal adjust- 

 ments would seem to be much slower than the fission, appearing to require for completion a day or two, 

 perhaps more in some cases. 



That this process of propagation is a normal one and of general occurrence during the summer can 

 hardly be doubted. The immense colonies which may often be found on a given stone, or on a shell of 

 Mytilus, could hardly have happened thus by other mode. Furthermore, when one seeks for perfectly 

 symmetrical specimens in a state of nature they are difficult to find. The figure shown in plate xxi, made 

 from a living specimen, illustrates the asymmetry in the single white line connecting the directive ten- 

 tacle of only one side. But this is not all. Sections of the body show the asymmetry to involve the 

 whole internal organization — mesenteries, siphonoglyphes, etc. 



In most ca,ses the species is normally diglyphic; but during the season of asexual propagation this 

 feature is more or less obscured or disguised. Further reference to figure i will make this point more 

 evident. I have occasionally found triglyphic individuals, but they are rather unusual. One such 

 was observed undergoing fission, and in this case the process involved very nearly an exact third of the 

 parent body, leaving an unsymmetrical diglyphic specimen. I was somewhat curious to see whether 

 a fission into three individuals at once might not occur, but this did not happen; and though the speci- 

 men was followed during two or three succeeding days there was no indication of further fission. 



Carlgren (1904) in a recent paper has described experiments and observations on several species 

 of actinians which have interesting features in common with those herein described. On page 77 he 

 gives some account of fission found occurring in nature, and certain of his figtires might be duplicated 

 by this phenomenon in S. lucicB (e. g., fig. 6, 24, 23, 26, 27, taf. I and n.) 



The mesenteries of this species vary greatly in number and arrangement. I had the privilege of 

 looking over a large number of sections made by Mr. D. W. Davis, who has been engaged in experiments 

 upon it, and sought in vain for a single case of what might be regarded as typical hexamerous symmetry. 



Distribution: The species was first described by Verrill in 1898. It was first observed at New 

 Haven about 1892, and was then quite rare. Within the past 10 years, to the personal knowledge of the 

 writer, the occurrence of the species at Woods Hole has passed from a condition of comparative rarity to 

 one of extreme abundance. A brief paper by Parker ( 1902) gives a succinct account of its dispersal along 

 the coast since its first occurrence about New Haven. Apparently the same species has been recently 

 found at Plymouth, England (1908), and a few brief comments made to the effect that instead of having 

 got its introduction into our region and spread from that as a center, the fact would seem to be that 

 it had found distribution from some unknown source and had been simultaneously scattered and estab- 

 lished in several remote localities. Mr. Davis has recorded the species at San Francisco, and states that 

 its identity with S. lucia: seems beyond question. I looked in vain for it at South Harpswell, Me., 

 in 1909." 



a The writer identified this species at Naples in 1911. having the same distinctive features of structure, color, mode of fission* 

 etc. This would seem to show that it is probably very widely distributed over the shallower seas. 



