38 Anatomy of Sagartia Schilleriana [No. 1, 



minute. In the fourth muscular layer, which chiefly consists of cross 

 fibres, there are at distances small round holes to be observed, which 

 evidently lead to the cinclides of the outer integument ; these holes are 

 often rather indistinctly traceable in the scleroid parenchym. 



My observation as to the presence of solid scleroid particles in the in- 

 ternal tissue of the Sagartia has, in the first instance, been made in con- 

 sequence of a simple process of maceration in water, and weak acid. It be- 

 came, however, important to test further the true nature of these different 

 scleroids. I consequently exposed a specimen, placed in a platina 

 crucible, to a heat sufficient to remove every trace of organic matter, and 

 was satisfied to find in it the residue of a perfect, solid skeleton of 

 the Sagartia, on which were seen externally the holes for the cinclides, 

 and, in being broken up, internally the septa. The external portions 

 appeared more fibrous, the internal more broadly cellular or reticular. 

 The character of the substance perfectly resembled the spongy and 

 irregularly cellular structure of the corallum of other reef-forming 

 AntJiozoa (see fig. 6, plate XI). A portion of this skeleton was then 

 placed in hydrochloric acid ; this operation shewing that the solid 

 skeleton mostly consisted of carbonate of lime, which is present in the 

 form of the long scleroids (pi. XI. fig. 5b) ; the flat angular parti- 

 cles, being of silica, remained unaltered (fig. 5c). The latter formed 

 a dark, very thin, irregular network, though most of them were loose, 

 and apparently irregularly distributed among the calcareous scleroids. 

 Besides the two kinds of scleroids, I observed a large number of 

 extremely fine, often branching threads ; but whether these belong to 

 the tissue of the coral, or to some species of sponges, I was unable 

 to ascertain. The proportion of siliceous scleroids to those consist- 

 ing of lime is not probably more than one to twenty. 



This direct proof of the secretion of solid scleroid particles in the 

 internal tissue of the Sagartia is very important, inasmuch as it will 

 in time, when more observations of this kind have been made, neces- 

 sitate a change in the characteristics of the so-called AntJiozoa mala- 

 coderonata. It would be premature and unjustifiable to state that all the 

 Sagartiidos, or other Actiniacea, possess an internal skeleton, as no other 

 observations have been yet made on this point. It is, however, to be 

 hoped that the present statement will induce stricter and more ac- 

 curate inquiry, especially as Mil. Edward, Blainville, and others, many 



