POEAMINIFERA OF THE KEEIMBA AECHIPELAGO. 877 



spicules arranged in a single layer with their axes arranged more or less parallel to the 

 long axis of the test. The ultimate chamber terminating in a somewhat produced 

 neck, on which is situated the aperture of the test, which is a circular opening. The 

 lines of demarcation between the separate chambers are marked by very slight sutural 

 depressions, but are principally recognisable owing to a divergence of the angles at 

 Avhiclr the spicules of adjacent chambers are arranged (fig. 18). The septation of the 

 internal cavity is very incomplete, but the different successive chambers are recognis- 

 able in section by these sutural depressions, which extend as an incomplete septum into 

 the cavity of the test. It follows that each of these incomplete septa must originally 

 have formed a portion of the external wall of the test which has been absorbed in the 

 course of growth, the spicules, no doubt, being rebuilt into the new investing wall. 



We first noticed this form more than twenty years ago in dredgings made by the 

 late Captain Seabrook, and given to us by our old friend and correspondent, the late 

 Mr. W. H. Harris of Cardiff. The dredgings in which the specimens occurred were 

 made off Cebu in the Philippine Islands (depth 120 fms. — volcanic mud) and in the 

 Java Sea (45 fms.). Identical specimens have since been observed in a dredging from 

 the Sahul Bank, in the Timor Sea (50 fms.), and in a dredging off Old Providence 

 Island in the Caribbean Sea (382 fms.). The peculiar and highly characteristic 

 construction of the test is the same in all these widely separated localities, and. as 

 sponge-spicules do not form any marked proportion of the bottom in any of the 

 dredgings, the "selective" tendency must be regarded as exceptionally pronounced — 

 almost as striking, in fact, as in our species Technitella thompsoni'*, which, from a 

 heterogeneous mass of available material, selects for the construction of its test 

 nothing but the plates of an Ophiurid. 



The skill — or "• purpose " — exhibited by this little organism in the building of its 

 test reaches its most remarkable development in the construction of the aperture. 

 The spicules designed to form the terminal portion of the shell are selected by the 

 organism of such size and shape as to form a perfectly tapered neck with a circular 

 aperture, round which the points of the spicules often form a regular fringe (figs. 17, 

 18, 20). It would appear that the organism utilizes only such spicules as are suitable 

 for its purposes owing to their tapering form, terminating in a sharp point, which 

 allows the size of the aperture to be considerably reduced, as compared with the size 

 which would have resulted from the utilization of broken or blunted spicules. The 

 spicules employed are invariably of a simple type, and this is very noticeable in the 

 Cebu specimens, as hexactinellid spicules abound in that dredging. 



Specimens occasionally (but not invariably) present two or three larger spicules 



* E. Heron-Allen and A. Earland. " Oa a new Species of Technitella from the North Sea, with some 

 Observations on Selective Power as exercised by certain Species of Arenaceous Foraminifera," Journ, Quckett 

 Micr. Club, ser. 2, vol. x. 1909, pp. 403-412, pla. xxxi.-xxxv. 



