7. Anthozoa (incl. Hydrocorallia). A. Zoantharia. 17 



from modern cyclical corals. In P. we have a living example in which the secon- 

 dary mesenteries and septa arise in the same manner as in many of the fossil corals. 



Appeliof describes the development of Urticina (Tealia) crassicornis and Actinia 

 equina. The ova of U. are discharged and develop in the water. They contain a 

 considerable quantity of yolk. The vitelline membrane remains to a late stage, 

 forming an envelope around the larva. The ova segment in a manner previously 

 unknown in Actiniae. The nucleus divides into 16 and meanwhile certain changes 

 take place in the nucleus, protoplasm and yolk, in virtue of which segmentation be- 

 comes possible ; the author considers that the retardation of cleavage is not entirely 

 due to the abundance of yolk. When 16 nuclei have been formed the protoplasm 

 (and larger yolk spherules which have retreated somewhat from the centre of the 

 ovum) become divided into 16 blastomeres which are arranged round the segmen- 

 tation cavity. The central portion of the ovum remains undivided and is found as 

 a somewhat viscous substance in the segmentation cavity. The peripheral portion of 

 each blastomere is almost free from yolk while the inner end is laden with large 

 yolk spherules ; during the later stages of segmentation the inner ends become se- 

 parated as non-nucleated pieces from the peripheral protoplasmic portion, and lie 

 in the segmentation cavity, the contents of which function as food yolk. The endo- 

 derm is formed by invagination and the yolk is transferred to the archenteron. - 

 In A. the blastocoel is also filled with food yolk which is formed principally by im- 

 migration of cells from the blastoderm but also partly by fragments of the inner 

 ends of blastoderm cells which have become detached from the blastoderm and 

 now lie in the segmentation cavity. The endoderm is formed by immigration of 

 cells from the blastoderm, and the mouth arises as a breach in the wall of the pla- 

 nula brought about by dissolution of the cells at this point. The lips of the opening 

 bend inwards forming the stomodaeum. - -In U. the lips of the blastopore become 

 invaginated thus forming the stomodaeum. The septa arise almost simultaneously, 

 or if there is a slight difference in their time of origin, no definite order of succes- 

 sion can be distinguished. No gastral chambers are visible until they are marked 

 out by the down-growing septa. The glandular streaks of the mesenterial fila- 

 ments are outgrowths of the epithelium of the stomodaeum and therefore of ec- 

 todermic origin. The ciliated streaks arise later and are likewise ectodermic. 

 The septal stomata appear late by resorption of the mesogloea. The sphincter 

 muscle also arises veiy late, at any rate after the muscular ridges on the mesen- 

 teries have been formed. In both U. and A. 8 tentacles arise simultaneously. In 

 A. there is no stage distinguishable by the occurrence of an unpaired tentacle, 

 as described by Lacaze-Duthiers and others. The author criticises the account given 

 by Duerden [see Bericht f. 1899 Coel. p 12] of the development of Lebrunia, and 

 thinks D. is in error in considering any part of the stomodaeal epithelium of endo- 

 dermic origin. The endoderm of L. does not consist, as D. states, of several layers, 

 but of a single layer, enormously thickened by the presence of numerous vacuoles, 

 and not representing a mesenchym. The author does not accept Goette's sug- 

 gestion that the Scyphistoma is a stage in the phylogeny of the Anthozoa. He 

 points to the condition seen in the larva of A. when the breach in the wall of the 

 planula has just taken place, and remarks that this is the simplest conceivable or- 

 ganisation a simple opening leading into the cavity surrounded by a two layered 

 wall. If this is not a secondarily acquired condition it seems probable that we 

 should look for the ancestral form of the Anthozoa among the Hydroids. 



Davenport records variations in the number of the orange coloured longitudinal 

 bands (usually about 12) of Sagartia Luciae. Longitudinal fission was observed in 

 which the 12 stripes were apportioned to the two resulting individuals as follows 

 9 + 3, 8 + 4, 7 + 5. Hence the variation in number of stripes in individuals is 



