410 E. HERON-ALLEN AND A. EAIILAND 



as clever. Our specimens from the Faroe Channel show a 

 marked tendency to vary the length of the spicular fragments 

 in contiguous lines, and in one specimen the spicules are " laid " 

 with a spiral twist like the strands of a rope. Such an arrange- 

 ment must be the result of design, and not of mere chance. 



(4) As a protection against enemies. There are certain 

 instances in which sponge spicules are employed by foraminifera 

 where their presence seems inexplicable, unless they are employed 

 for defensive purposes. Perhaps the best example is the curious 

 Ilalhphysema tumanoiviczii (Bowerbank), long regarded as a 

 sponge. This little organism grows in colonies on algae and 

 zoophytes, where it would be constantly exposed to the ravages 

 of mollusca browsing about. Each specimen completes its test 

 by the addition of a compact brush of sponge spicules which 

 radiate in all directions from the last chamber, and must form 

 an efficient chevaux defrise against prowling enemies. Polytrema, 

 one of the large perforate foraminifera which grows attached in 

 similar surroundings, has acquired the same habit. 



Defence is probably also the explanation in the case of the 

 extraordinary variety of Crithionina pisum (Goes), figured by 

 Flint under the name of hispida. Here the normally smooth 

 sphere of C. pisum, with its thick mud walls, becomes a 

 mass of sharp radiating points, due to the selection of long 

 sponge spicules, which are built into the wall so that they 

 project in all directions. Specimens of C. pisum and other 

 foraminifera with a small round hole in the side showing where 

 some predatory mollusc or other animal has broken through and 

 devoured the sarcode body are of frequent occurrence, but such a 

 defensive armour of spines would be an efficient protection, besides 

 perhaps acting as a raft or support to prevent the shell sinking 

 in the soft mud surface of the sea-bottom. 



There remains one method of employment of sponge spicules 

 which, if it can be the result of design, is rather puzzling. We 

 refer to the cases where a single sponge spicule is found trans- 

 fixing an arenaceous foraminifer (compare the figure of Psammo- 

 sphaera fusca (Schulze), in Brady's Report on the Foraminifera 

 of the "Challenger" Expedition, PL XVIII., Fig. 4). The 

 spicule may owe its position entirely to chance ; but it is quite 

 as likely, in view of the rarity of such specimens, that it was 

 designedly built into position. Such projections would be of 

 service to the animal by increasing the area of resistance and by 

 acting as a raft or spar, and so helping to keep the organism 



