ON A NEW SPECIES OF TECHNITELLA FROM THE NORTH SEA. 409 



(1) As building material pure and simple : entire or broken 

 spicules being worked into the wall of the test, apparently 

 without any intentional plan or design. Such examples may 

 be found in nearly all genera with composite tests wherever 

 sponge spicules form any appreciable proportion of the deposit. 



(2) To increase the strength of the test : spicules being 

 utilised either (a) as " joists " to strengthen the construction 

 of a test, or (b) as " laths " in a plaster wall, to retain the layer 

 of mud in position, and to strengthen and support it. As an 

 instance of (a) we may quote Sorosphaera confasa (Brady), which, 

 in the specimens dredged at " Goldseeker " Station 9, has built 

 its inflated chambers round large tetractinellid sponge spicules 

 which project irregularly from the outside and traverse the 

 chambers. Curiously enough the surface of the sponge spicules 

 within the chambers is covered with a thin laver of the ferruginous 

 cement used in the construction of the test. The object of this 

 is not clear, but presuming this layer to be one and continuous 

 with the lining of the test, it would serve to increase the strength 

 of the joist, as compared with a joist which was merely attached 

 to the wall at the points of entry and exit. As an instance of 

 (b) the case of Technitella legumen (Norman) already referred to 

 may be quoted. 



(3) As building material in preference to any other. Those 

 foraminifera which exercise marked discrimination in the selection 

 of building material usually select sponge spicules in preference 

 to any other material. I'echnitella melo (Norman) and Marsi- 

 pella cylindrica (Brady) afford perhaps the best instances. The 

 material has its disadvantages as well as its merits, for the 

 adhesion of the cement to the glassy surface of the spicule is but 

 slight, and where the spicules are cemented together so that 

 their ends come into a more or less direct line of joints, the risk 

 of fracture is greatly increased. There is a variety of the 

 common Annelid, Amphictene auricoma (Pectinaria), figured and 

 described by Dr. Mcintosh,* which utilises fragments of sponge 

 spicules for its conical tube instead of the usual sand-grains, and 

 we have specimens from the North Sea in which the fragments 

 are built together with a real bond, like bricks in a wall. 

 Probably no foraminifera ever attained to such skill in building 

 as this, but Marsipetta cylindrica (Norman) at its best is nearly 



* "On certain Homes or Tubes formed by Annelids," W. C. Mcintosh, 

 M.D., F.R.S., Ann. Mag. Nat. Hist. ser. 6. vol. xiii. January, 1894. 



