507 



the diverging canals for the most part terminate in the stolons of 

 communication between the segments of sarcode that occupy the 

 chambers of the outer whorl. 



The evidence afforded by the distribution of the canal-system in 

 Polystomella is decidedly confirmatory of the view expressed by the 

 author on a former occasion, that this peculiar set of inosculating 

 passages is related to the formation and nutrition of those solid 

 calcareous layers which strengthen and connect the proper walls of 

 the chambers, and to which he has given the designation of the 

 " intermediate skeleton." 



This view derives strong confirmation from the still more extensive 

 distribution and greater importance of the canal-system of Calcarina, 

 a genus of which Mr. Cuming's Philippine collection affords a most 

 remarkable series of illustrations. This type may be considered as 

 closely allied to Polystomella in the disposition and mode of com- 

 munication of its chambers, save that the spire is generally more or 

 less inequilateral. Its "intermediate skeleton" is, however, much 

 more developed ; and it extends itself into a variable number of pro- 

 longations, sometimes simply club-shaped, sometimes more or less 

 ramifying, which radiate in different directions from the central body, 

 giving it somewhat the appearance of a spur-rowel, whence its 

 generic designation. (An approach to this configuration is occasion- 

 ally presented by the common Polystomella crispa, as also by 

 some other species of Polystomella.) Now the independence of the 

 intermediate skeleton and of the spiral system of chambers is curi- 

 ously shown by the disproportionate development which they respect- 

 ively exhibit the one to the other, and by their occasional complete 

 disconnexion, the spire altogether departing from its usual course, 

 and (as it were) running wild, whilst the intermediate skeleton 

 with its prolongations still present their ordinary configuration. The 

 nutrition of the intermediate skeleton seems to be provided for by a 

 system of large canals, freely inosculating with each other, which 

 originate on the sides of the chambers, and are continued through 

 the whole thickness of the intermediate skeleton, some of them pass- 

 ing directly to its nearest surface, whilst others are continued to the 

 terminations of its radiating prolongations. 



It is not a little remarkable that a Foraminiferous organism should 

 present itself so extremely resembling the preceding as to be easily 



