22 Coelenterata. 



streift; doch 1st ein Unterschied zwisclien innerer und peripherer Substanz zu 

 machen. Die Meridionalstreifen setzen sich aus Wimperrinnen und Ruder- 

 epauletten so zusammen, dass die einen fiir die anderen vicariiren. Die Wimper- 

 rinnen gleichen embryonalen Ruderplattchen ; beides sind nur Modificationen 

 eines und desselben Gebildes. Auch an den Tentakeln hat Verf. weder Sinnes- 

 zellen noch Tasthaare gefunden (gegen H. etc.); die Greifzelleu liegen, sich 

 gegenseitig polygonal abplattend, dicht aneinander. 



6. Graptolitha.) 



7. Anthozoa (incl. Hydro corallia). 

 A. Zoantharia. 



See Combes, Cook, Crossland, Duerden(V> 6 ,V)> Forster-Cooper, Richet(V), 

 , 2 ), Vaughan, above p 8 Abric and below Mollusca p 15 Romer. 



For fossil forms see De AngelisJ 1 , 2 ), Dennant, Etheridge, Felix, Jakowlew, 

 Janensch, Rauff & Felix & Blanckenhorn, Simpson. 



Carlgren( 1 ) points out that there are two views as to the formation of the 

 first 8 tentacles in Actiniaria (1) that first a tentacle is formed over the dorsal 

 directive chamber (Actinia equina, Lacaze-Duthiers) or 2 over the 2 directive 

 chambers (Sagartia bellis, Lac.-Duth.) before the other 6 or 7 tentacles appear; 

 (2) that the first 8 tentacles arise simultaneously (Adamsia, Sagartia par asitica, 

 Faurot; Urticina, Appellof). The author found 2 embryos of Cribrina 

 (Bunodes) each with only one well marked tentacle and the others faintly 

 indicated, but numerous cases either with 2 opposite directive tentacles or with 

 the dorsal one longer than the others. He concludes that the first 8 tentacles 

 of C. arise almost simultaneously, but there is a distinct tendency for the 

 directive tentacles, especially the dorsal one, to make their appearance before 

 the others. In Peachia the first 8 tentacles arise almost at the same time, but 

 soon the directive tentacles are smaller than the others. The tentacles in P. 

 and C. are not all homologous, but only the 2 directive tentacles and the one 

 on each side of the dorsal tentacle; the remaining 4 are exocoelic in P., ento- 

 coelic'in (7., as is shown by later development. In Halcampa duodecimcirrata 

 tentacles 5.5 are as large as the first 8 before 6.6 appear, and there are 

 localities in the Baltic in which these forms apparently do not develop 6.6. 

 The small chambers produced by the formation of mesenteries 5.5 and 6.6 

 are more ventral in C. than in P. The arrangement of tentacles in the latter 

 agrees with that of a typical Edwardsia, that of P. differs from that of 

 Siderastraea in that in the latter the first tentacles (6) are exocoelic while in 

 P. there are 6 exocoelic and 2 endocoelic (but these 2 latter have a tendency 

 to remain smaller). There are 2 types of development of the 9th to the 

 12th tentacles. In the bilateral type ((7., S., H. and probably most Acti- 

 niaria) there arises on each side of the directive plane and on each side of 

 the ventro-lateral tentacle of the 8-tentacle stage, an exocoelic tentacle, the 

 more dorsal ones (5.5) rather earlier than the more ventral (6.6). In the 

 biradial type (P. , E. and others in \vhich the primary entoccelic are shorter 

 than the exocoelic tentacles) there are formed 4 tentacles, 2 on each side of 

 the directive plane, one on each side of the lateral tentacle of the 8-teutacle 



