REPORT ON THE DEEP-SEA MEDUSAE. lxxiii 



Medusa which detaches itself from the strobila (fig. K,fp.). Corresponding to this origin, 

 each filament consists of a solid (sometimes cylindrical, sometimes flattened) gelatinous 

 filament or fulcral papilla, which is simply a papillose or digital excrescence of the 

 supporting plate of the taeniolum. The endodermal epithelium of the latter passes directly 

 on to the filament and consists partly of flagellate cells, partly of glandular cells (calyx 

 cells) to which thread cells and (perhaps universally 1) delicate muscular epithelial cells are 

 often added (comp. PI. XXII. figs. 23-26). The movable gastral filaments of the Medusae 

 are usually simple, more rarely branched dichotomously or even pinnated (PI. XXVI. 



108. Phacelli, or groups of filaments. It is only in the simplest and oldest genera of 

 the Acraspedas {Tessera, System, taf. xxi.; Epliyra, taf. xxvii.) that the filamental 



Fig. H. Procharagma proiotypus (Cubomeduss, Charybdeidse). 



Horizontal transverse section below the stomach, whose subumbral wall (gc) is completely visible, in 

 the middle, the oral opening (a) with the four perradial oral lobes (al). The gastral filaments (/) 

 are placed upon the four interradial pyloric valves (gy). (gw) Subumbral wall of the two gastral 

 pouches (bp). (s) Genitalia, (ug) Gelatinous substance of the umbrella. 



products of the taeniola are limited to the simple gastral filaments (lying immediately on 

 the four interradial cathammal nodes), and also in the young larvae of other Acraspedae, 

 e.g., in the Ephyra larvae of Aurelia, there are at first only four such simple filaments 

 (fig. A, fix). In all other Acraspedae numerous filaments are present, which form separate 

 " groups of filaments " or phacelli. There are always originally only four interradial 

 phacelli (fig. D, f) ; these have arisen by division of the four originally simple fila- 

 ments, or by repeated production of filaments from the taeniola. Instead of the 

 four interradial, there are often eight adradial phacelli, which have arisen by bifurca- 

 tion of the former, and are, therefore, more accurately, four pairs of phacelli. These are 

 usually united in pairs at the proximal end, whilst they diverge at the distal end. The 

 distal division of the eight phacelli is strongest in the Periphyllidaa, where the four 



(ZOOL. CHALL. EXP. — PAET XII. — 1881.) M k 



