326 APPENDIX. 



signifying Toot-likc feet. Many of the species secrete shells, and 

 although the shell of a single animal may not be larger than the 

 point of an ordinary pin, it has pores or foramina through it which 

 give exit to the thread-like processes ; and the shells are therefore 

 called foi'aniinifers. 



Rhizopods occur often as solitary animals ; but generally, like 

 polyps, they multiply by budding, and thus make groups of cells, 

 some of the larger of which have the magnitude of a quarter of a 

 head of a pin ; of this nature are the Globigerime, and various 

 other kinds, cominon over the bottom of the deep ocean, as well as 

 in many shallow waters. A few form, through the budding process, 

 disk-like or coin-shaped foraminifers, half an inch to an inch in 

 diameter ; and such are the Orbitolites, referred to, ^n page 121, as 

 contributing largely to the coral reefs of the Austi. iian seas, while 

 common throughout the reef regions of the Pacific. 



In one division of Rhizopods — that including the Globigerinae 

 and Orbitolites — the foraminifers are calcareous ; in another, they 

 consist of agglutinated sand ; in another (that of the Polycystines^ 

 they are siliceous. 



In another section of Protozoans called the Flagellate Infusoria., 

 and including the Monad, there is a permanent mouth, and often a 

 slender process {^flagelliuji) which appears to serve the mouth by 

 pushing in food. The animals are much more minute than the 

 Rhizopods, To this section, as Prof. H. James Clark has shown, 

 belong the sponges — a sponge being a compound group of these 

 living infinitebimals produced by growth and budding. 



A third division of Protozoans is that of the Vorticellse and 

 related forms. They have at top a circle or spiral of cilia, around 

 a disk, in one part of which disk the mouth is situated. These 

 beautiful species — occasionally large enough to be visible to the 

 -naked eye — often grow in clusters resembling somewhat those of 

 the Hydroids and Bryozoans. 



