1915] on Beauty, Design and Purpose in the Foraminifera 477 



The Foraminifera are to be found in all parts of the world and 

 under all conditions, on the shore, in deep sea soundings and dredo-ino-s, 

 and floating at all depths of the ocean, whence they are taken in tow 

 nets, and they divide roughly into two great classes, the Calcareous 

 (SI. 20), which secrete from the surrounding waters a delicate and 

 beautiful shell of carbonate of lime, and the Arenaceous (SI. 21), 

 which build their shells out of sand-grains, sponge-spicules, and 

 other fortuitous materials, often affording remarkable indications of 

 phenomena of purpose and intelligence to which I shall presently 

 refer. A single species, Carterina spiculotesta (SI. 22), builds its shell 

 of fusiform calcareous spicules, secreted by the animal itself by a 

 process which is at present entirely obscure. A remarkable feature of 

 the organism is that whereas the resulting spicules on the upper 

 surface follow the convolutions of the chambers, on the under side 

 (SI. 23) they are turned inwards so as to converge towards the 

 central umbilicus. 



The distinction between the calcareous and arenaceous shells is 

 purely artificial, isomorphs existing between the three great classes, 

 the hyaline (or perforate), the porcellanous (or imperforate), and the 

 sandy (or arenaceous). A typical isomorphism (SI. 24) is represented 

 by the three genera Cornuspira, w^hich is porcellanous, Ammodiscus, 

 which is arenaceous, and Spirillina, which is hyaline. 



I will now show rapidly some of the most striking species to be 

 found in the sub -families of the order, beginning with the imperforate 

 porcellanous Miliolidai. 



Nuhecularia lucifaga (SI. 25) is a wild growing and usually 

 adherent form, which under its coarse and shapeless exterior has its 

 chambers arranged on the plan of several other genera. 



Biloculiiia serrata (SI. 26) is one of a genus in which the chambers 

 are arranged in regular pairs opposed to one another. 



SpirolocuUna nitida (SI. 27). In this genus the chambers are 

 spread out upon a single plane so that all are visible on either side. 



Jliliolina semimdum (SI. 28) is one of the commonest of our 

 shore species. The genus assumes a vast variety of superficial 

 decoration (SI. 29), one of the most striking being 31. hertheUniana. 



MassUina secerns (SI. oU) is one of our commonest forms, often 

 forming thick white bands and patches on our shore sands. 



In Cornuspira foUacea (SI. 31) the monothalamous shell is arranged 

 in a flat spiral. 



A typical arenaceous form is Saccammina sijhcBrka (SI. 32), among 

 the monothalamia, and Haplophragmium crass imar go (SI. 33), among 

 the polythalamia, which, broadly speaking, are either spirally wound, 

 or htuiform, as in H. pseudospircde (SI. 34), or with the chambers 

 alternating, as in Textidaria aggJutinans (SI. 35). 



Wehbina cJavata (SI. 36) clings to mineral or shell fragments, 

 cominunicating with the surrounding medium by a delicate tube. 



One of the most beautiful and delicate of the arenacea is Reophax 



Vol. XXI. (No. 109) 2 i 



