822 



MICROSCOPIC FORMS OF ANIMAL LIFE 



Author, however, from his own examination of the Globigerina ooze, 

 is of opinion that the shells forming its surface-layer must live on the 

 bottom, being incapable of floating in consequence of their weight ; 

 and that if they have passed the earlier part of their lives in the 

 upper waters they drop down as soon as the calcareous deposit con- 

 tinually exuding from the body of each animal, instead of being em- 

 ployed in the formation of new chambers, is applied to the thicken- 

 ing of those previously formed. That many types of Foraminifera 



pass their whole lives at 

 depths of at least 2,000 

 fathoms is proved, in regard 

 to those forming calcareous 

 shells, by their attachment 

 to stones, corals, &c. ; and 

 in the case of the arena- 

 ceous types by the fact that 

 they can only procure on th<' 

 bottom the sand of which 

 their ' tests ' are made up. 



A very remarkable type 

 has recently been discovered 

 adherent to shells and corals 

 brought from tropical seas, 

 to which the name Carpen- 

 ter ia has been given. This 

 may be regarded as a highly 

 developed form of Globi- 

 gerina, its first formed por- 



FIG. 621.-GloMgerina, as captured by tow-net tion having all the essential 

 floating at or near surface. 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 manner as to form a depressed 

 cone with an irregular spreading base, The essential character of 

 Globigerina the separate orifice of each of its chambers is here re- 

 tained 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, and is sometimes prolonged into a tube that proceeds 

 from it ; and the external wall of this cone is so marked out by 

 septal bands that it comes to bear a strong resemblance to a minute 

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

 principal chambers are partly divided into chamberlets by incomplete 

 partitions, as we s,hall find them to be in Eozoon. 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 was explained by the late Professor Max 

 Schultze, 1 who showed how the pseudopodia of this rhizopod have 

 the habit, like those of Haliphysema, of taking into themselves sponge- 

 spicules, which they draw into the chambers, so that they become 

 incorporated with the sarcode-body. It should be added that Pro- 

 1 Archivf. Naturgesch. xxix. 1863, p. 81. 



