ON A NEW SPECIES OF TECHNITELLA FROM THE NORTH SEA. 407 



foraminifer, and especially by that of a Technitella, one must 

 remember that the animal by which it was constructed was 

 but a tiny particle of protoplasm with a nucleus, having no 

 organs of any kind, whether alimentary, muscular, or nervous. 

 Notwithstanding this, there is a tolerably complete series, ranging 

 between (1) species in which the particles of building material 

 are simply piled together, without much order or definite arrange- 

 ment, through (2) other species, in which the separate particles of 

 building material are visible, but in which the joints are neatly 

 filled and " pointed " w r ith cement, to (3) species in which the 

 particles of building material are so small, and the quantity of 

 cement used so large, that the bricks are lost in the mortar, 

 so to speak, and a smooth, homogeneous surface results. The 

 cement used by the arenaceous foraminifera is of two kinds, 

 chitinous and ferruginous. The chitinous cement is usually 

 only visible as a film, on which the particles are cemented, but 

 the ferruginous cement, owing to its colour, is one of the most 

 striking features of the whole group. 



Owing to their elementary powers of locomotion, the arenaceous 

 foraminifera are limited in their choice of building material 

 to that which may be found constituting the sea-bottom in the 

 immediate neighbourhood of the spot in which they came into 

 existence, the probability being that they shift then* ground 

 but very little daring the course of their lives. It might be 

 supposed from this that all species from one locality would 

 present features in common, at any rate as regards " raw 

 material." Such, however, is not the case. Most species have 

 a certain range of construction beyond which they seldom 

 transgress, and they are constant to these characteristics in spite 

 of changed surroundings. Thus, in a single dredging in the 

 North Sea (" Goldseeker " Stn. 9) on a bottom of tenacious 

 sand and ooze teeming with life of all kinds, and in which 

 foraminifera especially abound, may be found species which 

 illustrate all the various steps in the ladder of selective power, 

 each taking from the constituent ground-mass just those materials 

 most suited to the construction of its particular test. Thus, 

 Astrorhiza limicola (Sandahl) takes material just as it comes, 

 shell fragments, sand-grains, or other foraminifera, and wattles 

 them together with mud into its characteristic roughly built 

 test, which, when completed, is so friable that it is seldom found 

 perfect in dried gatherings, though on cold sea-floors it is by 

 no means uncommon. Astrorhiza arenaria (Norman), on the 



