BILOCULINA. 93 



growth, or they may show ontogenetic variation, due to progression, or even to 

 deterioration of the special form. 



Although Foraminifera, like other organisms, should be classified on true 

 morphological characters, we all know it is good that the differences of individual 

 forms, and of limited groups of such varieties, should be carefully noted and made 

 serviceable to collectors and systematists ; and the only acceptable plan for the 

 purpose is (as has often been said) to apply the usual nomenclatorial terms, without 

 regarding them as of the same value as when applied to members of the groups 

 of higher animals. Keeping this in mind, we are glad to use the results of the 

 judicious and discriminative labours of MM. Munier-Chalmas and C. Schlumberger, 

 as in the case of earlier rhizopodal workers, and to give full references to their 

 descriptions and figures whenever fit opportunities occur. 



Clear and important remarks on this subject have been given by Dr. A. Goes 

 in the ' K. Svenska Vet.-Akad. Handl.,' vol. xix. No. 4, p. 7 ; and vol. xsv. No. 9, 

 p. 5, 



Genus 1. — BiLOCULiNA, d'Orbigny, 1826. 

 Part I, 1866, page 4. Brady's Report ' Challenger,' 1884, p. 139. 



Characters. — Chambers in one plane, embracing ; the last two only visible. 



We need not enlarge on the exact and philosophical treatment of this Forami- 

 niferal type by Williamson (1858) and Brady (1884), nor repeat the general 

 remarks published at pp. 4 — 6 of Part I. Biloculina multiplies itself in extremely 

 variable and gradational forms ; two of its most recognisable features are (1) the 

 slit-like aperture of B. ringens, and (2) the more contracted and somewhat pro- 

 jecting aperture of B. bulloides} The shape of the test varies from subglobose, 

 with two faces of varying inequality, to disciform or oval (thicker thin), lono--oval 

 or subcylindric, &c., each shape claiming a separate name with many authors. On 

 the external sculpturing and other ornaments, and sometimes on the constitution 

 and consistency of the test, other names are based. 



Of late the internal structure, so well studied by MM. Munier-Chalmas and 

 Schlumberger, has enabled them to recognise a greater fixedness in some of the 

 structural characters ; indeed, these observers have been able to systematise as 

 tangible species (if not genera) some forms regarded as varieties ; at the same time 

 we feel confident in relegating many of the " species," formerly so called, to mere 

 varieties of a type or sub-type. 



In the ' Svenska Vet.-Akad. Handl.,' vol. xix, 1882, pp. 131—134, Goes offers a 



1 See further on, p. 21. 



