PLANKTONETTA ATLAIMTICA. 133 



On Planktonetta atlantica, Borgert. 



By 

 O. Herbert Fowler, B.A., Ph.D., F.Z.S. 



With Plates 11 and 12. 



It is now many years ago that Ricliarcl Hertwig ^ founded 

 the group of Tripylarian Radiolariaus. Since that date 

 Haeckel " has added enormously to the list of known forms 

 in his monumental monograph ; yet but little attention has 

 been paid to the intimate structure of these curious organ- 

 isms. As there were several comparatively unbroken and 

 numerous broken specimens of an unusual Pha^odarian type 

 among the Plankton which I collected in the Bay of Biscay 

 on H.M.S. Research, in 1900, it seemed worth while to study 

 them somewhat more systematically than has usually been 

 the lot of members of this group. 



Dr. Borgert founded the species under the name of 

 Gazelletta atlantica'^ in 1901, giving a short preliminary 

 diagnosis and two cuts. Later on, he recognised the generic 

 differences between Gazelletta and the present form, and 

 established for it the name Planktonetta atlantica.^ 

 His material, however, was evidently considerably broken, 



' K. Hertwig, ' Dei Organisnius der liadiuhuitii,' Jena, 1S7'J, 4lo. 



- E. Haeckel, ' Cliall. Rep., Zool.,' " Tlie Kadiolaria." 



' ' Nordisclies Plankton, xv : Nordischen Tripjleen-Arten,' von Dr. A. 

 Borgert, p. 39. 



'' Borgert, " Mittbeilungen iiber die Tripjleeu-Ausbeute der Plankton 

 Expedition," ' Zool. Jalirbiiclien ' (Abtli. Syst.), xvi, 571. 



