REPORT ON THE ACTINIARTA. 21 



Edwardsire. The examination of the Challenger material has further confirmed the 

 correctness of this view, hut shows at the same time that the number of the varying 

 types is by no means exhausted. 



Most corals will doubtless be placed later on with the Hexactinise ; perhaps a natural 

 division into forms having a skeleton and forms without skeleton may not be possible, as 

 even the closer limitation of the Hexactiniae given here does not exclude the possibility of 

 many of their families having more affinity to single families of corals than to other Hexac- 

 tiniae. At all events it is advisable to keep this possibility in view in investigating corals. 



I shall discuss the families in an ascending series, according to the grade of their 

 organisation, and shall define the latter from two points of view. An Actinia is 

 placed lower down in the scale (l) the more uniformly the parts of the body are 

 developed, (2) the smaller the degree of histological differentiation. The first point 

 requires us to consider how far the septa resemble one another, how far the reproductive 

 organs are uniformly distributed, and so forth. From the second point we must keep in 

 view the nature of the muscular system ; is it preponderately ectodermal, endodermal, or 

 mesodermal, is there a circular muscle present and to what degree is it developed ? Further, 

 I consider the presence of the acontia, the cinclides, and the " bourses marginales " as 

 tokens of a higher organisation. Taken from this point of view, the Corallirnorphidse 

 are the lowest in every respect, the Sagartidse and Amphianthidse the highest. 



Family, Corallimorphid.e, R. Hertwig. 



Hexamerous Actiniae with a double corona of tentacles, a corona of marginal principal 

 tentacles, and a corona of intermediate accessory tentacles. Septa slightly differentiated, 

 all furnished with reproductive organs. Muscular system weak in all parts of the body. 

 No circular muscle. 



CoralUmorph us, Moseley. 



Corallimorphus, Moseley, 1877, Trans. Linn. Soc, ser ii., Zool., vol. i. p. 299. 



Marginal and intermediate tentacles knobbed and distinguished from one another by 

 their size. The largest tentacles correspond to the first cycle of septa, the smallest to 

 the last cycle of septa and to the interseptal spaces ; no terminal tentacle-openings 

 (perforations through the extremities of the tentacles, see p. 8). 



The family Coralliniorphidae is at present represented only by a single genus, 

 Corallimorphus, which was founded by Moseley for deep-sea Actiniae shortly after the 

 conclusion of the voyage of the Challenger, and divided into two species, Cored! imorphus 

 rigidus and Corallimorphiis profundus. It was considered most closely allied to Leuckart's 

 genus Discosoma (Ruppell, Reisc im nordl. Africa, 1828), and characterised as follows : — 

 " Body rigid, smooth, gelatinous, not contractile, without pores, but with an adherent base ; 

 disk circular and large ; tentacles non-retractile, elongate, conical, with a rounder! terminal 



