Heron-Ai-lkn AN11 KAiM.ANn — Stud/i of VeniciiUiiKi poliislrnjilui. 171 



absence of ferruginons material in theii* cement (figs. 34, 35). Not infre- 

 quently a test is brown (ferruginous) for tlie greater part of its length, and 

 then the later and latest chambers are white. In some gatherings also, and 

 especially among young tests, the organism abandons its smooth haliit, and 

 presents a rough exterior surface, the sand grains not being so carefully 

 arranged as to present a flat surface to the outside. 



We have made a close study of the form based upon a great number of 

 specimens, gathered from widely separated localities, and have also cultivated 

 a great many living specimens in our tanks at Selsey, and we have succeeded 

 in demonstrating that the species exhibits the phenomena of dimorphism 

 in {a) a long form, which is megalosplieric,*" and {h) a short form, which is 

 always microspheric.^' This demonstration was arrived at by means of 

 skiagraphs made for us by Mr. J. E. Barnard, f.k.m.s. The nature of the 

 test, and the extreme minuteness and obscurity of the primordial chambers, 

 made it impossible to produce satisfactory sections, but the skiagraphs, which 

 we illustrate, demonstrate clearly the dimorphism of the species (figs 49, 50, 

 on page 177). 



The megalospherie form [a) is long, blunt, and rounded at tlie aboral 

 extremity (or apex), and more or less parallel-sided in its growth, the taper- 

 ing being very gradual (fig. 6). The primordial chamber is large, spherical, 

 chitinous under a sandy investment (fig. 7), and sometimes divided into two 

 chambers by an internal chitinous septum (fig. 8). This megalospherie form 

 is textularian at the commencement. The normal triserial arrangement of 

 the chambers commences immediately after the first pair of chambers, the 

 second chamber being sometimes set by the side of, and flattened against, the 

 primordial. 



This subdivision of the primordial chamber by an internal septum (fig. 8) 

 is too striking not to be at once credited with a distinct biological signifi- 

 cance. It has already been noted by Wedekind in connexion with certain 

 species of Nummulites ; but he regarded it as being merely an abnormality 

 resulting from the primordial union of two individuals." The same pheno- 

 menon has been figured by d'Archiac, de la Harpe, and Pre\'er in other 

 Nummulites. Keferences to their figures will be found in an important 

 paper by H. Douville under the title " Les Foraminifferes sont-ils toujours 

 unicellulaires ? "" He deals at some length with the subject, and ascribes 

 ■the phenomenon to karyokinetic division of the prinunili.il nucleus, and 



^ Loc. cit. (note 7), PI. iv, fig. 1. "' Ihid., fig. 2. 



"- Scarfl' and Wedekind: " Dcr oberkarboue Sapropslit Spitzbergeu," Bull. Geol. 

 Inst. Univ. Upsala. vol. x, 1910-11, Nos. 19, 20, p. 103. 

 <» Comp. Rend. Ac Sci. Paris, vol, clxvii (1918), p. 140. 



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