40 Anatomy of Sagartia Schilleriana [No. 1, 



of the outer layer are of the same shape as those of the column, but 

 slightly longer ; the ecthoramm being about the same length as the 

 cell, or a little shorter and distinctly turned inside ; the largest cnidce 

 are not more than ^-g-^th of an inch in length (pi. XI, fig. 7). 



Below the mucous layer, there is a thin muscular, then a pigment, 

 and below this again a muscular layer (pi. X, fig Id). When the tenta- 

 cles shrink in a sickly or a dead specimen, they have the appearance of 

 thin, undulating threads, with a dark green centre, surrounded by a trans- 

 parent viscous layer ; the former representing the three inner, the latter 

 the mucous layer, with a large number of cnidce, (pi. XI, fig. la). 



In a full grown specimen there can usually be counted about 160 ten- 

 tacles, sometimes more ; but I have not been able to trace in a perpendi- 

 cular section more than five series of them. To illustrate the difference 

 in the increase of the septa, and in that of the tentacles, as I presume it 

 to be the case, I must direct attention to pi. XI, fig. 2, in which, on the 

 right half, the disposition of the former, on the left that of the latter 

 is shewn. The six primary septa meet, as I have formerly stated, in the 

 centre of the base, but are not traceable on the disc. The six primary 

 tentacles are seen to originate from each two tubercles of the lip, they 

 are distinguished from others by their great thickness, though in length 

 usually exceeded by the secondary ones. In the healthy animal they 

 often are of a light fleshy colour, especially.at their bases, and snow-white 

 towards the tips ; they are carried in a simple outward curve, generally 

 with their tips, leisurely moving about between the other tentacles, 

 which are more actively employed, .as already stated. Observed with 

 a moderately magnifying glass, the greenish and reddish pigment cells 

 can easily be traced out. The white tint of the tips is, I believe, only 

 due to a very large accumulation of cnidce, which appear to be arranged 

 in spiral rows, and become very distinct, when their inter-cellular sub- 

 stance is removed by its more rapid decomposition. On pi. X, fig. lc } 

 a representation is given of the tip of a primary tentacle, largely mag- 

 nified. The cnidce of this portion of the tentacles differ little in form 

 from others of the integument, except in their larger size, having at the 

 same time a proportionately thicker ecthoramm. Their fluid contents 

 is homogeneous, perfectly transparent, and the cell-membrane is rather 

 more tough, than in other cnidce. 



In very young specimens, the white tips at first appear on the 



