FAMILY GLOBIGERINIDA. 173 



it and with each other, producing either a spiral or some other figure, according to their 

 direction of increase ; whilst, on the other, the continuous tube of a Sjyirillina may contract 

 itself at intervals so as to form a succession of chambers, just as we have seen a Cortmspira 

 convert itself into a spiroloculine iI////o/rt (If 104). Now we find among the lowest of the 

 Polythalamous forms exactly such as might be the resultants of each of these modifications ; 

 for in Ghhigerinci we have a spiral aggregation of segments which are really disconnected 

 from each other, although united by mutual adhesion ; whilst in certain vermiculate forms 

 of the Rotalinc type we shall be very strongly reminded of what a SpirilHiia would be if 

 scgmentally divided at intervals by partial constrictions. 



274. In immediate structural relation to Globir/eriiw, but diverging from it in plan of 

 growth, we find the two small genera FuUenia and Spha-roidlna, of which the former, in the 

 finely poi'ous texture of its shell, and in the equilateral disposition of its spire, conducts us 

 towards the simplest " nonionine " forms of Polijstomella, a member of the family Nummu- 

 LiNiDA ; whilst the latter, though essentially " globigerine " in the character of its segments, 

 has them applied one to another in a manner that reminds us of some forms of the Milioline 

 type, to which it also bears a further curious resemblance in having its aperture furnished 

 with a kind of " valve. "^ — The Globigerine type evolves itself, however, without any departure 

 from its essential character, into a much more complex form, Carpenteria ; which, on the one 

 hand, presents us with a singular feature of approximation to Sponges, whilst, on the other, 

 it exhibits, in the duplication of its septal laminae, and in the presence of a canal-system, an 

 elevation of type which is not a little remarkable as based on a foundation so humble. 



275. Although we might very naturally pass from Ghhigerina to the Rotaline series, 

 yet it seems desirable, in the first place, to notice the Texttilarine ; because, although the 

 lower types of the two may be considered as on the same grade of development, the highest 

 types of the former rise far above those of the latter. The genera of which the Textularine 

 series is composed, are characterised by the alternating arrangement of their chambers upon 

 an elongated axis ; the successive chambers freely communicating with one another by 

 (usually) crescentic apertures ; but each being so applied to the preceding that the septum is 

 single, so that there are neither intraseptal spaces, intermediate skeleton, nor canal-system. 

 This group thus represents in its own series both the Uvigerine type of the vitreous-shelled 

 family Lagenida, and the Valvuline of the arenaceous Lituolida ; and its relationship to 

 the latter seems to be even more intimate than to the former ; since both in Te.vtidaria and in 

 Biillmina it frequently happens that the proper substance of the shell is replaced to a great 

 extent by an aggregation of sandy particles, in the midst of which, however, the pseudopodial 

 pores are still traceable. It is unquestionably in these aberrant modifications of their re- 

 spective series, that the great primary groups of Perforate and Imperforate Foraminifera show 

 the most intimate relationship ; the iijpivul forms of those groups, even when most resembling 

 one another in external configuration, being most completely differentiated in essential 

 characters. — In tlic ordinary Textularia the alternation of the chambers is essentially biserial; 

 but in some of its subgeneric modifications it is triserial, whilst, on the other hand, it may 

 become uniscrial. In Bidimuia, again, the chambers are disposed, without any definite 

 number, in a spire which strongly resembles that of a Bidiimts ; but in some of its subgeneric 



