REPORT ON THE ACTINIARIA. 31 



The twenty-four tentacles are of extraordinary length compared with the size of the 

 animal; the largest of them are 3-5 cm. long, whilst the smallest are only l"5-2"0 cm., 

 the six others being of medium length. The tentacles have precisely the same arrange- 

 ment as in the Corallimorphida), so that the largest of them correspond to the intraseptal 

 spaces of the primary septa, the six following to the intraseptal spaces of the secondary 

 septa, and the twelve smallest communicate with the remaining interseptal spaces in the 

 periphery of the oesophagus.. 



We may therefore assuredly assume, from this distribution of the tentacles, that the 

 septa are arranged exactly on the same principle as in the other Hexactinise. This is 

 corroborated by the distinct presence of two oral angles in the mouth, and two oesophageal 

 furrows on the oesophagus. I was, however, only able, from personal observation, to 

 ascertain that the septa are arranged in pairs, and that all the twenty-four bore repro- 

 ductive organs. 



The muscular system is nowhere mesodermal, the muscular lamellae are, moreover, 

 nowhere thickly pleated, either in the septa or in the tentacles and oral disk. The circular 

 muscle is consequently entirely wanting. 



Family, Anthead^e, Gosse. 



Hexactinias with long marginal tentacles and slightly developed endodermal circular 

 muscle (so that the oral disk cannot be covered at all, or only incompletely) ; numerous 

 septa, reaching for the most part up to the oesophagus, distinguished only by their size, 

 and all (?) furnished with reproductive organs. 



The family of the Antheadae, of which the well-known Anthea cereus is the typical 

 representative, was erected by Gosse. Owing, however, to my having limited it here on 

 the basis of a more exact anatomical definition, it differs in extent from that given in 

 Gosse 's well-known work. On the one hand, I have separated from it the genus Aiptasia, 

 which has acontia and cinclides, following Verrill, who was the first to declare this 

 necessary (Comm. Essex Inst., vol. v. p. 322, 1866-7), whilst, on the other hand, I have 

 no hesitation in incorporating in this family the Actiniae with rough surface of the body, 

 inasmuch as they fulfil the above-mentioned conditions, whilst Gosse considers the 

 smooth surface of the wall as the most important characteristic. 



According to my own observations, Anthea cereus has marginal spherules, though 

 these do not strike the eye by their bright colours, so that we cannot separate the An- 

 theadae from the Actinidae furnished with marginal spherules, on account of absence of 

 these formations ; it therefore becomes a question whether it would not be more to the 

 purpose to follow Verrill and unite the two families (Trans. Connect. Acad., vol. i. p. 491, 

 1867-71). As my own experience has shown that the nature of the circular muscle in 

 Actinia mesembryanthemum approaches that in Anthea cereus, I am inclined to answer 



