FORAMINIFERA OF NORTH PACIFIC OCEAN. 9 



the last-formed chamber of the adult. There is also a tendency for 

 the last-formed chamber to surround the preceding, ones either 

 entirety, as in Orbulina, or in part, as in some of the species of Globi- 

 gerina. Some of the species develop very long spines on the surface 

 of the test. Most of the species also develop a spherical or nearly 

 spherical test which, as has been shown by Rhumbler, is the form 

 which requires the least amount of secretion to cover the animal. 

 In the matter of the size of the perforations also there is a difference, 

 even in species of the same genus, between those living at the surface 

 and those on the bottom, those of the surface forms being several 

 times as large as those of the bottom ones. In general, while the 

 various structures mentioned are also found in the bottom spe- 

 cies to some extent, they are strikingly characteristic of the pelagic 

 Foraminifera. 



Evidently the pelagic character has been developed independently, 

 as there are members of three or more families represented. The 

 structures which they have developed in common, therefore, are to 

 be regarded as parallelisms due to similar environmental conditions. 



FOOD. 



In general, the food of the Foraminifera consists of vegetable mat- 

 ter, the diatoms and algae of various sorts furnishing the greater 

 part. In some of the pelagic forms, however, it has been observed 

 that copepods are caught and eaten, and some other Protozoa are 

 also caught. 



COLLECTION AND PRESERVATION. 



For one living near the ocean it is very easy to obtain material for 

 making a preliminary study of the Foraminifera. On stones, on the 

 piles of wharves and bridges, in fact upon almost anything that is 

 stationary for any length of time in the salt water, the Foraminifera 

 will be found in greater or less quantity. In the sand of tide pools 

 many species may be found, and in the sand dredged from a few 

 fathoms there are sure to be some tests present. If locality is not 

 important, and one merely wishes to become acquainted with the 

 various forms, they may be found in the sand from sponges, from the 

 "chain lockers" of ships, etc. 



For the study of a definite region involving any considerable depth 

 of water a special dredging apparatus must be used, together with 

 the various appliances used in deep-sea work. As such methods are 

 too elaborate for individual work as a rule, it must be left largely to 

 government vessels and to especially equipped scientific expeditions. 

 For getting together material for the study of a definite fauna, such 

 as that of the North Pacific, it is necessary to depend almost wholly 

 upon the work of such specially equipped vessels. The samples that 



