Foraminifera from the North Sea, etc. 387 



minute flakes of mica, rarely using any other material. Reophcvxftisi- 

 formis (Williamson) also makes considerable use of larger flakes. 

 But as a general rule, and in spite of its abundance in most muddy 

 dredgings, the use of mica is avoided by arenaceous Foraminifera. 

 The reason is fairly apparent after examining a large series of 

 specimens of Psammospluvra Bowmanni. The smooth surface of 

 the flake offers but a weak attachment for the cement, with the 

 result that the flakes are readily detached from the shell. 



We have much pleasure in associating this curious little form 

 with the name of Dr. Alexander Bowman, Assistant to Professor 

 D'Arcy W. Thompson, C.B., the Director of the North Sea Investi- 

 gations Committee (Scotland), in acknowledgment of his many 

 kindly services rendered in connexion with the dredgings made 

 by the ' Goldseeker.' 



Sub-family Rhabdamminin^. 



Marsipella Norman. 

 3IarsipeUa spiralis sp. n. 



Test free, monothalamous, consisting of an undivided tube, 

 which is built up of minute fragments of sponge spicules embedded 

 in a light grey cement, and arranged transversely to the long axis 

 of the tube. The spicules are built in a single layer, and have a 

 distinctly spiral arrangement when the specimen is examined 

 either as an opaque object or in a balsam mount. Viewed as an 

 opaque object under a 12 mm. objective, Marsipella spiralis looks 

 exactly like a piece of white string. 



The protoplasm is dark brown in colour, and appears to run 

 the entire length of the tube. 



Marsipclla spiralis is one of the most interesting species we 

 have met. The use of sponge spicules, either entire or fragmentary, 

 as building material is of Irequent occurrence in the Foraminifera, 

 but we know of no other species, except its near relative, 3Ia7'si- 

 pella cylindrica (Brady), and TechniteUa hfjvmen (Norman), in which 

 sponge spicules are employed in a manner or for purposes which, 

 in any organism of higher development than the Foraminifera, 

 would presuppose " intelligence " on the part of the builder. 



The sponge spicules employed by Marsipella spnralis are almost 

 without exception fragments. They are selected of practically 

 uniform length, • 06-0 • 1 mm., and arranged at angles between 30° 

 and 45° around the tube. The spiral is always left-handed. It is 

 obvious that the strength of the tube is greatly increased by the 

 spiral arrangement of the spicules ; indeed, Marsipella has made 

 the same great discovery as the man who first observed that a 

 twisted string was stronger than an untwisted wisp of fibres. 



Marsipella spiralis is confined to a limited area, so far as our 



