FORAMINIFERAN AND OTHER CORALS 177 



common word in our language which really conveys the 

 correct idea of their general form and structure is the word 

 " coral." 



Many of the multilocular shells of the Foraminifera have 

 a spiral form similar to the shell of the pearly Nautilus 

 and some of its fossil relatives, and it was this resemblance 

 in form which led D'Orbigny into the error of supposing 

 that the Foraminifera were microscopic Cephalopods. The 

 discovery of the protoplasmic consistency of the body and 

 of the delicate network of pseudopodia they emit was made 

 by Dujardin, who definitely and correctly placed them in 

 the division Rhizopoda of the great group of unicellular 

 animals called the Protozoa. 



PoLYTREMA. — The most familiar and probably the most 

 abundant of all the Foraminiferan corals is Polytrema. It 

 has usually the form of a short branching coral-like structure 

 4-5 mm. in height attached by a flat and sometimes spreading 

 base to a foreign body. It has generally a pink or carmine- 

 red colour, but white varieties have been found in many 

 localities. It has a wide distribution in the warm and 

 tropical waters of the Old World and Pacific Ocean, but, 

 strange to say, is very rare in the West Indies and tropical 

 waters of the Eastern American coasts. It is extremely 

 abundant in the Mediterranean Sea, being found attached to 

 corals, zoophytes, to the leaves of Zostera, and to Algae of 

 various kinds. In some places broken, water-worn, but some- 

 times remarkably perfect specimens form an important con- 

 stituent of the sands cast up on the shore. Among the most 

 remarkable of these sands are the " sables rouges " near 

 Ajaccio off the coast of Corsica, which owe their red colour 

 to the vast numbers of whole or fragmentary specimens of 

 Polytrema. It was in these sands that Mr. Heron-Allen dis- 

 covered the rich material for his description, to which refer- 

 ence will presently be made, of the important stages in their 

 life-history before and after fixation to a foreign substance. 



The first description of Polytrema is that given by 

 Pallas in 1766, who classified it with that heterogeneous 

 medley of corals called Millepora by the older writers. It 

 had previously been seen by Tournefort (1700), who made 



N 



