FUNICULINA QUA.DRANGULARIS. 



It 13 thus seen that the thickest part of the stem is at the point 

 where the fleshy coenenchjm is thinnest; indeed, as is seen from the 

 measurements fjiveu above, the total thickness at this point — the 

 junction of rachis and stalk— is due almost entirely to the stem, which 

 is here covered by a layer of ccenenchym so thin that the quadrangular 

 shape of the stem is evident on mere inspection. 



A point of much greater interest, and one on which we think some 

 stress should be laid, is that the proportions of the stem at various 

 points of its length are such as, mechanically considered, to adapt 

 it most perfectly to what we regard, for the i-easons stated above, as its 

 normal position, i.e., planted erect with the stalk buried in mud and 

 the rachis projecting freely above it into the water. In this position the 

 thickest and strongest portion of the stem is at the point where most 

 strength is needed, i.e., at the surface of the mud. The gradual 

 tapering downwards in the first part of the stalk gives a firm, rigid 

 support, wt ile the gradual and steady tapering towards the upper end 

 of the rachis provides the requisite strength in the lower part with 

 increasing flexibility in the upper. So marked, indeed, is this 

 adaptation of the shapa of the stem to the form of the whole Pen 

 that it would alone be an argument of no inconsiderable weight in 

 favour of the erect position being the natural one. 



The lower part of the stem is very stiff, rigid, and brittle ; the 

 upper part is highly flexible, so that the two ends of the stem may be 

 brought together without the slightest danger of breaking. 



The stem itself, when freed from the coenenchyin, preserves the 

 very graceful curve already referred to, and well shown in Fig. 2, 

 which is drawn from the largest of the three perfect specimens of 

 stems dredged up. 



Of the sixteen fragments of stems obtained, one 12 ins. in length 

 and with scarcely any ciu'vature, must, from its size, have belonged to 

 a specimen at least as large as, and probably larger than, the big 

 living specimen. The other fragments belonged, so far as we can judge, 

 to specimens averaging from 18 ins. to 36 ins. in length. In the curva- 

 ture and relative proportions of its parts the stein of Funiculina offers a 

 marked contrast to that of Virgularia, which we shall describe in a 

 subsequent section of this report. The differences are important, as 

 they appear to be directly connected with certain very marked 

 differences in the habits of the two genera. 



Transverse sections through the stem show that it consists of a 

 central core which is chitinous and only very imperfectly calcined, and 

 an outer very hard, and firmly calcified rind, with a smooth outer 

 surface, and made up of parallel lamellfe. As the stem grows in 

 thickness by the addition of successive lamellse on its exterior, and as 

 the proportions between the hard outer rind and the soft core are much 

 the same in both young and old specimens, it is clear that the process 

 of deposition of calcareous lamella) on the outside must be accom- 

 panied by absorption of the calcareous matter previously deposited in 

 the more central portion. 



