STACHE1A. 109 



may be joined end to end more or less compactly, or may be connected by delicate tent- 

 like stoloniferous tubes, single or brandling ; or each individual segment may represent 

 an entire animal, the test soiiK'timrs having an aperture placed at the end of a tadpole- 

 like tail, sometimes having no visible orih'ce. The adherent rougher Lituolte have 

 received the sub-generic name Plaeopailina, and they present much the same range of 

 morphological variation as the adherent Troclutmiidine, but they are always coarse and 

 rough in shell-texture. The segments are also usually more closely packed, and in 

 early growth they show a tendency to take a spiral arrangement. The trochoid and 

 plano-convex species of Vulvulina appear to be all constructed for parasitic growth, but 

 except the very conical forms they are seldom found actually adherent. 



The genus Pofypkreyma 1 represents typically an irregularly cylindrical, sub-arenaceous 

 test, attached by one end, and growing in a curved or nearly erect line. It is composed 

 of a single series of superimposed discoidal segments, the aperture taking the form of a 

 number of perforations, arranged in more or less regular rings, on the convex face of the 

 terminal chamber. 



Turning now to the PERFORATA, in the first division (family Lagenidd), the genus 

 Polymorphina alone presents adherent forms, and these appear as aberrant modifica- 

 tions of well known free varieties. In the Polymorphina concava of Williamson the 

 adhesion is effected by the convex side of the shell, whilst in the " rooted " forms 

 figured in the Monograph of the genus, 2 the attachment is secured by the fistular shelly 

 outgrowths. 



In the family Globifferinida the most prominent parasitic types are Carpenteria, 

 Planorbulina, and Polytrema, though the smaller Discorbina and perhaps other plano- 

 convex and trochoid Rotalians may occasionally be found growing upon foreign bodies. 



Carpenteria is essentially an irregular encrusting Globiyerina, its relationship at times 

 attested by a disposition to assume a spiral arrangement in some of its segments ; but 

 more frequently consisting of a confused mass of chambers with large conspicuous 

 perforations. The plano-convex and outspread Planorbulirue are probably normally 

 parasitic, as well as a section of the sub-generic group Truncaiiilina ; and even the allied 

 genus Tinoporw possesses an adherent variety, noticed on a later page as an isoruorph of 

 one of the varieties of Stacheia. 



"Of all Foraminifera " observes Dr. Carpenter (Introd. p. 235) "there is none so 

 decidedly Zoophytic in its form and habit as Polytrema, for although it sometimes spreads 

 itself on the surfaces of shells, corals, &c., it not unfrequently rises from those surfaces in 

 an arborescent form, whilst sometimes its stalk instead of branching, swells into a globular 

 protuberance, which leaves a strong resemblance in size and general aspect to the 



1 Polyphragma cribrotum, Reuss, 18/2, ' Das Elbthalgebirge in Sachsen,' Her Theil, p. 139, pi. 

 figs. 8-10. 



2 Brady, Parker, and Jones, 'Trans. Linn. Soc. Loud.,' vol. xxvii, pi. xlii, figs. 38, i,j. 



