88 



THE MICROSCOPE AND ITS REVELATIONS. 



previously formed. That many types of Foraminifera pass their whole 

 lives at depths of at least 2000 fathoms, is proved, in regard to those 

 forming Calcareous shells, by their attachment to stones, corals, etc. ; and 

 in the case of the Arenaceous types, by the fact that they can only pro- 

 cure on the bottom the sand of which their ' tests ' are made up. 



481. A very remarkable type has 



Fi s- 327. recently been discovered, adherent 



to shells and corals brought from 

 tropical seas, to which the name 

 Carpenter ia has been given; this 

 may be regarded as a highly devel- 

 oped form of Globigerina, its first- 

 formed portion having all the es- 

 sential characters of that genus. 

 It grows attached by the apex of 

 its spire; and its later chambers 

 increase rapidly in size, and are 

 piled on the earlier in such a man- 

 ner as to form a depressed cone 

 with an irregular spreading base. 

 The essential character of Globi- 

 gerina the separate orifice of each 

 of its chambers is here retained 

 with a curious modification; for the 

 central vestibule, into which they 

 all open, forms a sort of vent whose 

 orifice is at the apex of the cone, 



d is : sometimes prolonged into a 



tube that proceeds from it; and the 

 external wall of this cone is so mark- 



ed-out by septal bands, that it comes to bear a strong resemblance to a mi- 

 nute Balanus (acorn-shell), for which this type was at first mistaken. 

 The principal chambers are partly divided into chamberlets by incomplete 

 partitions, as we shall find them to be in Eozoon ( 494). The presence 

 of sponge-spicules in large quantity in the chambers of many of the best- 

 preserved examples of this type, was for some time a source of perplexity; 

 but this is now explained by the interesting observations made by Prof. 

 Mobius 1 on a large branching and spreading form of Carpenteria, which 

 he recently met-with on a reef near Mauritius, and to which he has given 

 the name of C. raphidodendron. For the pseudopodia of this Rhizopod 

 have the habit, like those of Haliphysema ( 474), of taking into them- 

 selves sponge-spicules, which they draw into the chambers, so that they 

 become incorporated with the sarcode-body. 



482. A less aberrant modification of the Globigerine type, however, 

 is presented in the two great series which may be designated (after the 

 leading forms in each) as the Textularian and the Rotalian. For not- 

 withstanding the marked difference in their respective plans of growth, 

 the characters of the individual chambers are the same; their walls being 

 coarsely-porous, and their apertures being oval, semi-oval, or crescent- 

 shaped, sometimes merely fissured. In Textularia (Plate xv., fig. 14) 

 the chambers are arranged biserially along a straight axis, the position 

 of those on the two sides of it being alternate, and each chamber opening 



Globigerina, as captured by tow-net, floating 



at or near surf ace. 



1 See his " Foraminifera von Mauritius," Plates v., vi. 



