524 PROF. GILBERT C. BOURNE ON FIVE 



than tentacles. I think there can be no doubt that Faurot's specimen 

 had not attained its full growth and full complement of tentacles. In the 

 two living specimens of E. tiniida kept under careful observation by 

 G. Y. Dixon (6) there were respectively 20 and 22 tentacles. In bbth 

 specimens of this species that I studied by means of sections there were 

 twenty-four tentacles and twenty-four mesenteries. Dixon^s specimen with 

 twenty tentacles, referred to by him as yS^, was abnormal ; but Jiis specimen 

 with twenty-two tentacles exhibits an arrangement perfectly consistent 

 with what I have observed. Jn Dixon's aa. specimen the arrangement 

 of the tentacles is the same as in E. rakaiyw, but a quaternary tentacle has 

 made its appearance on the dorsal side of the primary tentacle in each of 

 the dorso-lateral megacoeles. At least, this is what I surmise has taken 

 place, because in both njy specimens of E. timida the largest number of 

 tentacles and mesenteries is in this megacoele — so I have taken the liberty 

 to reverse Dixon's figure. He only studied the li\ing animal, and could not 

 tell, except by sections, which was the dorsal and which the ventral aspect 

 of the animal. 



In my two specimens of E. timida the tentacles are twenty-four in number, 

 and there are the usual eight macromesenteries and sixteen micromesenteries. 

 As studied in sections, the tentacles are obviously of different lengths, and, 

 though the relative lengths are not always a safe guide to the age of tentacles 

 in Actinians, I do not think I am wrong in assuming that the conspicuously 

 longer and larger tentacles in these specimens were formed earlier than the 

 shorter and smaller, especially as both specimens give the same results in this 

 respect. Each of the directive megacoeles is prolonged, as usual, into a 

 single primary tentacle. The dorso-lateral megacoele gives off five tentacles, 

 of which the two outermost, respectively nearest the dorsal and dorso-lateral 

 macromesenteries, are conspicuously longer than the others. Within them 

 are two very short tentacles and in the centre a long tentacle, which is clearly 

 the primary. The probable order of appearance of these tentacles is indicated 

 by the numerals in text-fig. 1. In each lateral megacoele there is only a 

 single micromesentery separating two unequally-sized tentacles. Of the 

 latter the dorsal is decidedly the longer, and must be identified with the 

 primary tentacle. My specimens have therefore a smaller number of 

 mesenteries and tentacles in the lateral megacoeles than Dixon's, though 

 more advanced in other respects. In the ventro-lateral megacceles there 

 are three mesenteries dividing the peripheral part of the megaccele into 

 tour microcoelic chambers, from each of which issues a single tentacle. 

 That nearest the ventral directive is large ; the next one to it is small; then 

 follows a large tentacle ; then a small one, next to the ventro-lateral macro- 

 mesentery. In this chamber it is obvious that a quaternary tentacle has 

 been formed on the ventral side of the primar}^ 



