12 Coelenterata. 



Roulef 2 ) describes Palythoa paguricola which is commensal with Pagurids. Each 

 colony consists of 3 or 4 individuals connected by ccenosarc. The zooids are of two 

 sizes, the larger, 2 in number, being placed one on each side of the crab's body. 

 The central part of the colony consists of a ccenosarcal sac which envelops the 

 crab's abdomen, is open at one end and at the other bears the 1 or 2 small polyps 

 of the colony. The mesogloea contains numerous sand grains which give to the 

 polyps and to the coenosarc, thin though it be, a consistency which enable them to 

 protect the soft abdomen of the crab. Very likely the larve becomes fixed to a 

 small shell inhabited by the young Pagurid, and as the former grows its base 

 spreads over the shell, finally covering it with a coenosarcal lamina. The shell then 

 disappears by resorption brought about by the coenosarc and thus the Pagurid and 

 the P. reach the condition seen in the specimens described. 



Carlgren(') describes the external characters and principal anatomical and histo- 

 logical features of the following East African Actiniae Cerianthus 1 n., Bolo- 

 ceroides 2 (1 n.), Corynactis 1, Edwardsiella 1, Alicia 1 n., Isactinia n. 1, Gyrostoma 

 3 n., Ammonia 1 n., Actinoides 2 n., Bunodes 2 (1 n.), Phellia 1, Isophellia n. 1, 

 Calliactis 1, Discosoma 3 (2 n.), Phymanthus 3 (2 n.), Stoichactis 2, Helianthopsis 

 2 (1 n.), Antheopsis 1, Thalassianthus 2 (In.), Heterodactyla 1, Actinodendron 1 n., 

 Zoanthus 2 n., Isaurus 1, Gemmaria 3 n., Palythoa 3 n. The author gives details 

 of the distribution and size of the nematocysts believing them to be of some value 

 in the identification of species and genera. As a rule thin-walled nematocysts in 

 which the spiral thread is visible are found only in the tentacles and in the oral 

 disc, in some species also in the body (column) wall and stomodaeum. Thick-walled 

 nematocysts are found in all parts of the ectoderm; their length is moderately 

 constant in the species; as a rule the largest ones are found in the stomodaeum, 

 slightly smaller ones in the tentacles, while those in the oral disc and in the foot 

 are smallest. But when outgrowths of the body wall are present, these generally 

 bear the largest nematocysts. Stuhlmann observed that in living specimens of Gy- 

 rostoma tristis after wounding in any place a large number of small tentacles is there 

 produced. The author discusses the classification of the Actiniaria and taking 

 account of the internal anatomy and of the great changes in the organisation brought 

 about according as the muscles for contracting the body longitudinally are peri- 

 pherally or more centrally placed, proposes the following groups: A) Protantheae : 

 1) Protactininae (not to be confounded with the Protactiniae of Me Murrich), 2) 

 Protostichodactylinae ; B) Nynantheae: IjActininae; 2)Stichodactylinae. The tribe 

 Protantheae is defined as follows: "Actiniaria with a layer of longitudinal muscle 

 fibres in the body (column) wall and generally also in the stomodaeum. Ganglionic 

 layer of the ectoderm of the body wall usually well developed. Proximal end of 

 body usually flattened and foot-like but always without basilar muscles. Filaments, 

 as a rule, without ciliated streaks. Without acontia, verrucae on the body wall 

 and cinclides. Sphincter absent or very weak and then always endodermal." The 

 Prot. are distinguished from the higher forms (Nynantheae) principally by the oc- 

 currence in the former of longitudinal muscles in the body wall and by the absence 

 of basilar muscles. The Nynantheae have, during their phylogeny, gradually 

 lost the longitudinal ectodermic musculature which has been replaced by the longi- 

 tudinal muscles developed in the mesenteries, the foot has become a creeping sole 

 and basilar muscles have been developed, and along with an increase in the number 

 of mesenteries ciliated streaks have appeared on the mesenterial filaments. The 

 lowest forms of both Actininae and Stichodactylinae agree in several important 

 points, both being provided with longitudinal ectodermic muscle fibres, and being 

 without basilar muscles and "Flimmerstreifen". The Stichodactylinae com- 

 prise 7 families. - - A) Without basilar muscles, "Flirnmerstreifen" and gonidial 



