PROTOZOA : FORAMINIFERA. 



75 



larger divisions, and a single series in another, but often amongst several 

 series even of the same family. It not unfrequently happens that a mem- 

 ber of one group presents a greater similarity to its isomorph in another 

 group with which it has no relationship, than it does to any other member 

 of its own group. Take a familiar illustration suppose the fingers of the 

 two hands to represent the modifications ('species') of two such parallel 

 types of Foraminifera : the thumb of one hand resembles more closely the 

 thumb of the other hand than it does any other of the fingers on its own. 

 In other words, the extreme member of one series resembles more closely 

 its isomorph in the other series than it does its own nearer relations, and 

 so on through the remaining members of the respective groups. Under 

 conditions like these, artificial subdivision, based upon minor morpholo- 

 gical characters, is certain to infringe the order of nature. Its tendency is 

 to separate forms closely allied, and in many cases to place together such 

 as have no close affinity." 



DISTRIBUTION OF FORAMINIFERA IN SPACE. The 

 ifera (save Gromia, which occurs in both fresh and salt water, 

 and the fresh-water forms allied to this) are marine, and are found 

 in almost all seas, though more abundantly in those of the warmer 

 parts of the globe. It is concluded by Dr Carpenter that " the 

 foraminiferous/tf#;/tf of our own seas probably presents a greater 

 range of variety than existed at any preceding period; but 

 there is no indication of any tendency to elevation towards a 

 higher type."' One of the most remarkable facts about their 

 distribution at the present day, 

 is the existence of a deposit at 

 great depths in the Atlantic 

 and Pacific oceans, in areas 

 traversed by warm currents, 

 of a mud or "ooze" formed 

 almost entirely of the shells of 

 Foraminifera, and principally 

 of Globigerincs (fig. 15). This 

 " Globigerina ooze " is found 

 up to depths of 3000 fathoms, 

 and may be regarded as the 

 modern analogue of the white 

 Chalk of the Cretaceous period. 

 The deep-sea dredgings of late 

 years have further brought to 

 light an immense number of 

 forms of " arenaceous " Fora- 

 minifera of the most varied and interesting characters. Some 

 of the living Foraminifera may be obtained, at or near low- 

 water mark, adhering to the roots of tangle; but they are 

 mostly to be obtained by dredging in deeper water, or by the 

 tow-net, or by search in the shelly sand of the sea-shore, 



Fig. 15. Organism 

 chiefly Foraminifera 



in the Atlantic ooze, 

 'igerina and 



Textularia), with Polycystina, and 

 Sponge - spicules ; highly magnified. 

 (Original.) 



