GENTS CALCAEINA: INTEENAL STEUCTTJEE. 555 



continued into the spines where these are given off from it ; whilst others pass not 

 less directly towards the two convex surfaces of the disk. In the earlier whorls of the 

 spire, as shown in Plate XX. figs. 2 and 7, indications of spiral canals, commencing (as 

 in Polystomella, ^[188) in a central lacunar system, are frequently traceable; and 

 sometimes we may make out a general distribution of the canal-system of the earlier 

 whorls (fig. 7) that strongly reminds us of that prevailing in Polystomella (^f 189), the 

 canals of the spines originating (as seen at a) in diverging branches which radiate outwards 

 through the spaces left between the two layers of the septa. But this arrangement 

 soon seems to be merged, as it were, in the much more copious distribution of passages 

 that arise from the lacunae round the proper walls of the chambers. The canals which 

 pass towards the two surfaces of the disk soon lose the general uniformity of arrange- 

 ment which they elsewhere present ; for they become crowded together in some situa- 

 tions and separated in others, so as to leave a number of columnar spaces untraversed, 

 whilst the intercolumnar spaces are copiously penetrated by them, as is seen at e, e, e, 

 in Plate XX. figs. 1 and 5, the one figure showing the solid columns divided longitudi- 

 nally, and the other showing them as they are cut transversely. The varying appear- 

 ances of the external surface, as described in ^f 199, will now be understood. When, 

 as commonly happens, the summits of the columns rise above the general level of the 

 surface, they will show themselves as rounded tubercles. But when they are not thus 

 elevated, they will merely be distinguished as circular spots surrounded by the puncta- 

 tions which are the orifices of the canals. In the spines, on the other hand, the canals 

 form a longitudinally inosculating system (Plate XX. fig. 2), of which the branches near 

 the surface usually reach it so obliquely as to pass along it for some distance as open 

 furrows (^[ 200), the punctations seen in which are the orifices of branches that strike 

 the surface at a greater angle. 



205. It is obvious from the foregoing description, that the statement of M. D'OEBIGNT 

 as to the prolongation of the chambers into the spines is altogether erroneous ; and it is 

 further obvious that the nutrition of the spines must be provided for either through the 

 investment of their surface by external prolongations of the sarcode-body, or through 

 the penetration of its substance by prolongations of the sarcode-body conveyed into it 

 by the canal-system, or through both methods jointly. That the sarcode-body is con- 

 tinued in the form of pseudopodial prolongations into the canal-system can scarcely be 

 doubted, when it is borne in mind that such prolongations are known to pass through 

 the pores which are scattered through the chamber-walls of Eotalia, and to extend 

 themselves through the surrounding medium. After having made their way through 

 the proper walls of the chambers of Calcarina, they will probably coalesce again in the 

 lacunar cavities on the exterior of these, just as they coalesce to form a continuous layer 

 of sarcode over the chamber-walls oiEotalice or Polystomellce ; and from the aggregation 

 of sarcode in those cavities a new set of pseudopodial prolongations will take their 

 departure through the canal-system of the " supplemental skeleton," just as a secondary 

 set of pseudopodial filaments of sarcode are often seen to diverge from the little agglo- 



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