INTRODUCTION. XXI 



tip, where it passes off. BalanophylUa presents an excep- 

 tion to this rule, which I have found to hold good in all 

 other examined cases. In this instance, the tentacles, which 

 are densely clothed with palpocils, seem to me destitute of 

 external cilia, while all the scarlet parts are furnished with 

 these latter. The ciliary currents flow down the sides of 

 the column, and up the conical mouth from the whole 

 circumference of the disk. 



6. Reproductive System. The Actinaria increase by 

 spontaneous fission, by gemmation, and by generation. 

 Fission takes place either by a longitudinal division of the 

 entire animal from above downwards, or by separation of 

 small fragments from the edge of the base, which soon 

 develop themselves into minute and apparently young indi- 

 viduals. The former mode appears to be not uncommon 

 with Anihea cereus (see infra, p. 169) ; and an imperfect 

 form of the same produces double-disked individuals of 

 Actinoloba and Actinia. The latter mode is common with 

 several of the Sagartiado?. (see pp. 19, 66, 86, 110). 



Gemmation, — the production of buds from the parent 

 individual — occurs largely in the order before us, but prin- 

 cipally in those which have a stony skeleton. According to 

 Mr. Dana, whose classification I have followed, the Astr^e- 

 acea always bud from the disk, the Cartophylliacea 

 invariably from the side or base. But a specimen of 

 A. dianthus has come into my possession, — through the 

 kindness of L. T\ interbotham, Esq. of Cheltenham. — which 

 has two young individuals projecting one from each side, 

 at about mid-height, — an indubitable example of lateral 

 gemmation. The animal has continued in the same condi- 

 tion for nearly a year, with no tendency to separate its 

 progeny. 



Generation is of course the normal mode of increase of 

 the race. The sexes are sometimes united in one indi- 

 vidual (S. troglodytes, p. 100) ; sometimes separate (Stom- 

 phia Church ice, p. 225). The testes and the ovaries cannot 

 be distinguished from each other by a cursory examination ; 

 each consists of a pulpy mass, usually of an orange or pale 

 salmon-colour, attached to the free edges of the septa. The 

 peritoneal membrane which invests each side of the septum 

 is produced beyond the muscular layers in the form of 

 a mesentery of two films in contact (Plate XI. fig. 1, e). 

 At some distance from the edge of the septum, the films 



