Girvanella and the Foraminifera

Abstract

BULLETIN No. 104 of the United States National Museum contains the first part of Mr. J. A. Cushman's “Foraminifera of the Atlantic Ocean.” Workers in this group will find it of much value to have a complete and well-illustrated account of the foraminifera as occurring in the Atlantic. In this paper there is, however, one doubtful point in regard to affinity in which two distinct organisms are confused, and this, if not corrected, will mislead the student. I refer to the relegation of Brady's Hyperammina vagans to the genus Girvanella, Nicholson and Etheridge. It is a generally accepted opinion that Girvanella is probably related to the blue-green algæ (Cyanophyceæ), as shown by Rothpletz, Wethered, Seward, Garwood, and the writer. In the earliest descriptions Nicholson and Etheridge, it is true, held Girvanella to be of foraminiferal affinities, and Brady compared it to H. vagans, but the consensus of opinion is now in favour of its plant origin. As I have elsewhere shown (Aust. Assoc. Adv. Sci., Adelaide, 1907), its larger dimensions, arenaceous shell-wall, bulbous primordial chamber, simple, not branching, tube, and absence of septation separate it from Girvanella. In following Rhumbler (1913), Cushman includes other species of thread-like rambling and attached organisms. Whether they are all foraminiferal or algal in affinities can be determined only by careful examination by means of microscope sections, at the same time bearing in mind that the structure of the true Girvanella tube is not a mosaic of particles held by cement, but a finely granular structure such as is seen in other living calcareous algæ. The point here raised is directed against the placing of the genus Girvanella, as defined by Nicholson and Etheridge, with the Foraminifera.