PROTOZOA 



19 



Genera. — Tiwypwus, Carpenter ; Gypsina, Carter ; Apkrosina, 

 Carter ; Thalamopora, Roemer ; Polytrema, Risso. [Shell para- 

 sitic, encrusting, or arborescent ; surface areolated, coloured pink 

 or white. Fig. XII. 9. Interior partly occupied by small chambers, 

 arranged in more or less regular layers, and partly by non- 

 segmented canal-like spaces, often crowded with sponge-spicules 

 No true canal system. This is one of the most important types as 

 exhibiting the arborescent and encrusting form of growth. It is 

 fairly abundant.] 



a 



FlO. XII.— Perforata. ' 1. Spiral arrangement of simple chambers of a 

 Beticnlarian shell. 2. Ditto, with double septal walls, and supple- 



mental shell-substance (shaded). 3. Diagram to show the mode in 



which successively-formed chambers may completely embrace their pre- 

 decessors, i. Diagram of a simple straight series of non-embracing 

 chambers. 5. Hastigerina (Globigerina) Murrayi, Wyv. Thomson. 

 a, bubbly (vacuolated) protoplasm, enclosing b, the perforated Globi- 

 gerina-like shell (conf. central capsule of iladiolaria). R'om the peripheral 

 protoplasm project, not only fine pseudopodia, but hollow spines of 

 calcareous matter, which are set ou. the shell, and have an axis of active 

 protoplasm. Pelagic ; drawn in the living state. 6. Globigerina 

 buliMes, D'Orb., showing the punctiform perforations of the shell and 

 the main aperture. 7. Fragment of tlie shell of Globigerina, seen 

 from within, and highly magnified, a, fine perforations in the inner shell 

 substances ; i, outer (secondary) shell substance. Two coarser perfora- 

 tions are seen in section, and one lying among the smaller. 8. Or- 

 bulina universa, D'Orb. Pelagic example, with adherent radiating 



calcareous spines (hollow), and internally a small Globigerina shell. It is 

 uncertain whether Orbulina is merely a developments! phase of Globi- 

 gerina. a, Orbulina shell ; 6, Globigerina shell. 9. Polytrema minia- 

 ceum, Lin. ; x 12. Mediterranean. Example of a branched adherent cal- 

 careous perforate Eeticularian. 10. Calcariiia Spengleri, Gmel. ; x 10. 

 Tertiary, Sicily. Shell dissected so as to show the spiral arrangement of 

 the chambers, and the copious secondary shell substance, a^, a^, a*, 

 chambers of three successive coils in section, showing the thin primary 

 wall (finely tubulate) of each ; b, b, b, b, perforate surfaces of the primary 

 wall of four tiers of chambers, from which the secondary shell substance 

 has been cleared away ; c', c', secondary or intermediate shell substance 

 in section, showing coarse canals ; d, section of secondary shell substance 

 at right angles to c' ; e, tubercles of secondary shell substance on the 

 surface ; /,/, club-like processes of secondary shell substance. 



ObderIO. NUMMULINIDEA, Brady. 



Characters. — Test calcareous and finely tubulated ; typically 

 free, many-chambered, and symmetrically spiral. The higher 

 modifications all possess a supplemental skeleton, and canal system 

 of greater or less complexity. 



Fam. 1. FUSTJLININA. Shell bilaterally symmetrical ; chambers 

 extending from pole to pole; each convolution completely enclosing 

 the previous whorls. Shell-wall finely tubulated. Septa single or 

 rarely double ; no true interseptal canals. Aperture a single 

 elongated slit, or a row of small rounded pores, at the inner edge 

 of the final segment. 



Genera. — FusuUna, Fischer ; Schwagerina, Mbller. ■ 



Fam. 2. Polystomellina. Shell bilaterally symmetrical, nauti- 

 loid. Lower forms without supplemental skeleton or interseptal 

 canals ; higher types with canals opening at regular intervals along 

 the external septal depressions. 



Genera. — Nonionina, D'Orb. ; Polystomella, Lamarck. 



Fam. 3. Nitmmuhtina. Shell lenticular or complanate ; lower 

 forms with thickened and finely tubulated shell-wall, but no inter- 

 mediate skeleton ; higher forms with interseptal skeleton and com- 

 plex canal system. 



Genera. — Archseodiscus, Brady ; Amphistegina, D'Orb. ; Oper- 

 culina, D'Orb. ; Heterostegina, D'Orb. ; Nummulites, Lamarck ; 

 Assilina, D'Orb. 



Fam. 4. Cyoloolypeina. Shell- complanate, with thickened 

 centre, or lenticular ; consisting of a disk of chambers arranged 

 in concentric annuli, with more or less lateral thickening of lami- 

 nated shell substance, or acervuline layers of chamberlets. Septa 

 double and furnished with a system of interseptal canals. 



Genera. — Cydoclypeus, Carpenter ; Orbitoides, D'Orb. 



Fam. 5. Eozoonina. Test forming irregular, adherent, acervu- 

 line masses. 



Genus. — Eozoon Dawson. 



Further remarks on the Reticularia. — The name Thalamophora, 

 pointing to the peculiar tendency which the larger members of 

 the group have to form chamber after chamber and so to build up 

 a complex shell, has been proposed by Hertwig (56) and adopted by 

 many writers. The old name Foraminifera (which did not refer 

 to the fine perforations of the Perforata but to the large pseudo- 

 podial aperture leading from chamber to chamber) has also been 

 extended by some so as to include the simpler Gromia-like forms. 

 On the whole Carpenter's term Reticularia (62) seems most suitable 

 for the group, since they all present the character indicated. It 

 has been objected that the Radiolaria are also reticular in their 

 pseudopodia, but if we except the pelagic forms of Reticularia 

 (Globigerina, Orbulina, &c.), we find that the Radiolaria are really 

 distinguishable by their stiffer, straighter, radiating pseudopodia. 

 No doubt the Labyrinthulid Chlamydomyxa and the plasmodia of 

 some Mycetozoa are as reticular in their pseudopodia as the 

 Reticularia, but they possess other distinctive features which 

 serve, at any rate in an artificial system, to separate them. 



The protoplasm of the majority of the Reticularia is unknown, 

 or only very superficially observed ; hence we have made a point of 

 introducing among our figures as many as possible which show this 

 essential part of the organism. It is only recently (1876) that 

 nuclei have been detected in the calcareous-shelled members of the 

 group, and they have only been seen in a few cases. 



The protoplasm of the larger shell-makiug forms is known to be 

 often strongly coloured, opaque, and creamy, but its minute struc- 

 ture remains for future investigation. Referring the reader to the 

 figures and their explanation, we would draw especial attention to 

 the structure of the protoplasmic body of Hastigerina (one of the 

 Globigerinidea) as detected by the "Challenger" naturalists. It 

 will be seen from Fig. XII. 5 that the protoplasm extends as a rela- 

 tively enormous "bubbly" mass around the shell which is sunk 

 within it ; from the surface of this " bubbly " (vacuolated or alveol- 

 ated) mass the pseudopodia radiate. 



The reader is requested to compare this with Fig. XIII., repre- 

 senting the ' ' bubbly " protoplasmic body of Thalassicolla. It then 

 becomes obvious that the perforated central capsule CK of the latter 

 holds the same relation to the mass of the protoplasm as does the 

 central perforated shell of Globigerina (Hastigerina). The extreme 

 vacuolation of the protoplasm in both cases (the vacuoles being 



