Miscelliineous. 375 



cycles' (10, 10, 20, 40, 80) on tho coasts of Normandy, and only 

 four cycles (10, 10, 20, 40) on the English coasts*; but I attach 

 little importance to this fact. 



As to the number of tentacles in each cycle, it deserves careful 

 examination ; if anomalies exist, if certain individuals escape from 

 all rule, it is none the less evident that one may point out archetypes 

 for the greater number of species. 



1. The type M'ith G tentacles and its multiples (12, 24, 4S, &c.) is 

 the commonest ; it is this that has induced some observers to sup- 

 pose that all the Actiniae were derived from it. Prom the obser- 

 vations of Air. Gosse, and from my own, this type exists in about 

 twenty Actinia} of the European seas. The Banodes, among others, 

 may be considered as perfect Hexactinia). 



2. The type with 8, and multiples of 8, tentacles is very frequent. 

 It is indicated for nine species, to which, probably, the Cerianthi 

 may be added. 



3. The ty|)e with 10 tentacles is only seen in Tealia felinaf. 



4. Pahjthoa sulcata alone has 11 tentacles. 



5. These various t}qics combine among themselves ; thus the for- 

 mula of Edwardsia carnea would be 8, 8, 12, and that of Corynactis 

 viridis IG, 24, 32, 32. 



6. Lastly, there exist indetcraiinate tj-pes ; must we refer to type 

 6, 12, &c., or to a type 9, 18, and its miiltiples, the two following 

 species — Anemonia sidcata (3G, 36, 3G, 72) and Ui/anthus MitchelU 

 (18, 18) ? What is the type of Aureliania angusta, of which the 

 marginal series is composed of 42 tentacles ? Fah/tJioa Coitchi has, 

 according to my observations, 2 cycles of 14-15 tentacles. Mr. 

 Gosse attributes to it 24 tentacles (12, 12) in the young, and 28 

 (14, 14) in the adults, Avhich would prove that at one time this 

 species is a Hexactinia. 



These facts make one think that, in the zoological group of the 

 Actiniae, the number of tentacles has not the value that has been 

 attributed to it. The type has not even the importance of a generic 

 character, since in the genera iSagartia, FhelUa, Ualcampa, and 

 Edwavdsia certain species have 8, and others 12 tentacles and their 

 multiples. 



The variabilit}' of the number of tentacles is explained by the 

 cmbryogeny of the Actinia), the embryo having successively 4, 6, 8, 

 10, and 12 dissepiments and tentacles. By assuring an arrest of 

 development at each of these periods, we obtain the various types 

 which correspond to them ; and in certain species the normal com- 

 bination of the two types (Edivardsia carnea and Corynactis viridis) 

 faithfully represents the normal development of a Hexactinia, which 

 passes fi-om 8 to 12 dissepiments and tentacles. Seeing how much 

 the tentacular type varies in the Actinia?, one may also doubt the 

 importance of the number of systems and cycles in the Corals. 



* In the same way Sagartia sphyrodeta has 5 cycles (8, 8, 16, 32, 64) 

 on our coasts, and 4 cycles in England (8, 8, 16, 16), according to Gosse. 



t L. Agassiz has discovered iu America a species {Rhodactinia Dosvisii) 

 of the same type. Its embryos have 10 tentacles only. 



