REPORT ON THE ACTINIARIA. 1 1 



the animal is very irregularly developed ; the number of marginal tentacles amounts to 

 fifty-six, larger and smaller generally alternating ; two cycles, each of twenty-eight, might 

 thus be recognised, did one not consider that the tentacles of each cycle differ markedly 

 and somewhat irregularly in size. One is compelled to rank under the primary circlet, 

 tentacles which in diameter are far short of tentacles of the second order. Even more 

 irregular is the arrangement of those tentacles which are situated on the disc : their 

 total number, twenty-three, falls into three cycles, six tentacles being placed near the 

 mouth (oral tentacles), ten near the edge (peripheral tentacles), and seven intermediately. 

 Despite these apparently irregular numbers, I have noticed the complete validity of a 

 law in one-half of the animal, and it is of importance that this regular half commences 

 with the one pair of directive mesenteries and reaches to the other, thus just completing 

 one side of the animal. In the half in which a regular arrangement is followed, we 

 have three oral, six intermediary, and six peripheral, accessory tentacles. The six inter- 

 mediary alternate with the six peripheral, three of them standing on the same radius 

 as the oral tentacles. If we compare with these the marginal tentacles, the larger 

 twelve are on the radii already occupied by the tentacles on the disc, while the smaller 

 twelve are placed on the intermediate radii. At each of two points two tentacles are 

 present, a larger and a smaller ; and, being out of accord with the law which governs 

 Actinias, are either a token of the commencement of further growth, or constitute a case 

 of those numerous abnormalities which occur in the group. 



In the other half of the animal occur important gaps in the ground plan just 

 quoted. The three oral tentacles are in the same place as in the other half, (one is over 

 the chamber bounded by the directive mesenteries), but five of the intermediary 

 tentacles and two of the peripheral are wanting. The single intermediary tentacle 

 occurs in the region bordering on the directive mesenterial chamber just mentioned ; 

 this region is normally arranged, the peripheral tentacles being also present on it. As 

 with the tentacles on the disc, so also the marginal ones exhibit great irregularities ; their 

 number amounts to twenty-eight ; in size their relations are also variable, so that the 

 rule, that larger and smaller tentacles alternate, is in places infringed. 



The peculiar results of a macroscopic examination induced me to cut out a sextant 

 of the animal for a closer study by means of sections, choosing that sextant of the 

 normal side which contained the directive septa, and which only departed from the 

 regular scheme of the Hexactinise in the presence of two supernumerary tentacles. The 

 results were, that the mesenteries are grouped in pairs by the arrangement of their 

 muscles thus, — one pair of directive mesenteries, and four other pairs, all of which reach 

 to the stomatodseum. Of these four pairs I reckon one in the second cycle, two in the 

 third, the remaining pair being developed asymmetrically and repeating the irregularity 

 already noticed in the tentacles. 



From the intra-mesenterial chamber of the directive septa are evaginated three 



