CHAP. LI. ] TENERIFFE TO SOMBRERO. 211 
ism, probably an Alga; in which latter case the coccoliths and 
rhabdoliths might be regarded as representing in position and 
function the “amphidisci” on the surface of the gemmules of 
Spongilla, or the spiny facets on the zygospores of many of the 
Desmideze. There are many forms of coccoliths and rhabdoliths, 
and many of these are so distinct that they evidently indicate 
different species. Mr. Murray believes, however, that only one 
form is met with on one sphere; and that, in order to produce 
the numerous forms figured by Haeckel and Oscar Schmidt, all 
of which, and many additional varieties, he has observed, the 
spheres must vary in age and development, or in kind. Their 
Fie. 50.—A ‘*Rhabdosphere.” From the surface. Two thousand times the natural size. 
constant presence in the surface-net, in surface water drawn in 
a bucket, and in the stomachs of surface animals, sufficiently 
proves that, like the ooze-forming foraminifera, the coccoliths 
and rhabdoliths, which enter so largely into the composition of 
the recent deep-sea calcareous formations, live on the surface 
and at intermediate depths, and sink to the bottom after death. 
Coccospheres and rhabdospheres have a very wide, but not an 
unlimited, distribution. From the Cape of Good Hope they 
