7. Anthozoa (incl. Hydrocorallia\ A. Zoantharia. ^9 



is sexually mature as some of the sperm vesicles open on the side of the 

 mesentery and some of the ova have worked their way to the surface of the 

 mesentery ready to be discharged. The adaptation of this Cerianthid to pelagic 

 life is evidenced by the absence of coloration, translucence of the tissues and 

 feeble, development of gland cells in the body Avail. Its close relationship to 

 Dactylactis is shown by absence of buccal cone , arrangement of buccal appen- 

 dages, terminal (not lateral) insertion of the marginal tentacles, absence of 

 pores at the tip and on the inner face of the tentacles, relatively large direc- 

 tives, great length of the fertile mesenteries of the third couple, development 

 of the hyposulcus and the structure of the body wall and mesenteries. 



Hahn finds that the dimorphism in Metridium is due, not to alternative 

 inheritance of the diglyphic and monoglyphic coniitions, but to the frequent 

 occurrence of asexual reproduction. This takes place spontaneously by basal 

 fragmentation and may readily be induced by cutting off pieces of the pedal 

 disc. A directive system is regularly produced in the regenerated portion of 

 the young polyp, and if the portion derived from the parent already contained 

 a directive system, the young polyp will have two such systems and will be 

 diglyphic. If the fragment contained no directives, the young polyp will only 

 have the directive system produced in regeneration and will be monoglyphic. 

 The prevailing asymmetry and extreme variability in number and arrangement 

 of the mesenteries of H. may be explained by the method of development in 

 asexual reproduction. Triglyphic polyps and those with two or more oral discs, 

 with double or branched oesophagus or without siphonoglyphs are abnormalities 

 probably due to regeneration from fragments of unusual size and shape. 



Krempf( 1 ) holds that the Stichodactylinse contain two series of different forms, 

 the only common feature of which is the radial disposition of the tentacles. 

 CorynactiS) Discosoma and Rhodactis possess coral characters - - they have no 

 differentiated siphonoglyph and no septostomes, the mesenterial filaments have 

 no lateral lobes, the ovaries have few large ova, the musculature is feebly deve- 

 loped and the nematocysts have the form characteristic of those of corals. In 

 Stoichactis and Pkymanthus there is a siphonoglyph, septostomes are present, 

 the mesenterial filaments bear lateral lobes, the ovaries contain numerous ova, 

 the musculature is well developed and the nematocysts are like those of ordi- 

 nary Actiniae. The law of Milne-Edwards & Haime relative to the appearance 

 of the septa beyond the 4 th order applies entirely to the development of the 

 mesenteries in (7., D. and R. Specimens of these 3 genera were always found 

 to possess, when groAving on a surface covered with a calcareous alga, a thin 

 chitinous lamina separating them from the alga, and the ectoderm had under- 

 gone a double change, some of the cells having withdrawn themselves into the 

 mesogloea forming small degenerating masses, while the other ectoderm cells 

 had become transformed into elongate prismatic calicoblasts, with bundles of 

 deeply-staining fibrils, quite comparable to those of Hexacorallia. The skeleton, 

 however, is formed by only a single layer of calicoblasts, and is absent in 

 specimens fixed to a naked rock. The author Avould place the Stoichactidse, 

 Phymanthidse, Heteranthida?, Thalassianthida?, Actinodendridse and Aurelianidse 

 in the Hexactinise, but the Coralliinorphidse and Discosomidje in the Hexacorallia. 



Krempf( 2 ) examined three specimens of Hdianthopsis ritteri which had respec- 

 tively 5, 10 and 19 well-marked siphonoglyphs, none of these specimens seemed 

 to be preparing for division. He also records Bunodes 2, Phellia 1, Calliac- 

 tis 1, Triactis 1, Antheopsis 2, Stoichactis 2, PhymantJms 1, Zoantlms 2 n. var., 

 Palythoa 1, Cerianthus 1, Corynactis 1, Rhodactis 1, Discosoma 1, Stichopathes 1. 



Jennings describes the feeding of Stoichactis helianthus. The captured food 



