36 Anatomy of Sagartia Schilleriana [No. 1, 



siderable thickness, according to the different series to which they 

 belong. The twelve ovarian strings, or reproductive organs, can be 

 seen through the transparent skin ; and equally easily traceable are the 

 six bundles of the craspeda, in position nearer to the centre of the 

 axial cavity than are the former. 



b. The column represents the peripherical portions of the mesen- 

 terial folds, grown together, and it will, therefore, be sufficient to give 

 a detailed statement of the structure of one of the septa. The origin- 

 al number of these, as represented in the view of the basis (pi. X. fig. 

 5), is six, radiating from the centre. The second cicle is again six, 

 the third, fourth, and fifth are each twelve, one septum first appearing 

 next adjoining the primary septa, then one next to the secondary ones,, 

 than again one between the two last ones. This is a common law in all 

 Hexacorallia, and I only notice it here, because I will subsequently 

 draw the attention to the difference, apparently existing between the 

 increase of the septa and that of the tentacles. The septa of 

 the first, and usually also of the second, cicle are distinctly traceable 

 almost up to the centre, those of the 3rd and 4th nearly so, both 

 being about equal in strength, but those of the 5th are consider- 

 ably shorter. I have not observed in any of the numerous specimens 

 which I have examined, a larger number of cicles than five, or 48 

 septa altogether ; small specimens often had only three or four cicles 

 developed. The various cicles are shematically represented in figure 

 2 of plate XI. 



Each septum is composed of five distinct layers, as represented in 

 the enlarged section, plate XI, figure 3-a /3, y, 8, e. The outermost 

 a is, as formerly noticed, almost only a mucous fluid, composed 

 of a loose cellular substance, and a very large number of elongated 

 nettle cells, or cnidce, and a few dispersed cells of greenish pigment. 

 The cnidce of this mucous layer are, compared with others, the 

 shortest, being ovately elongated, slightly curved or kidney-shaped, 

 having, as a rule, an ecthoraeum, shorter than their own length ; 

 they also appear to be nearly smooth. — Figure 4 of plate XI 

 represents the appearance of the mucous layer under the micros- 

 cope, and 4« three-isolated cnidce still more enlarged. — The next 

 layer (jS) is strongly muscular, chiefly consisting of concentric or 

 cross fibres, forming at intervals slightly elevated ridges which 



