1915 215 F. A. Bather — Studies in Edrioasteroidea. 



action, their lack of pores prevents the extension of the hypothesis to 

 them. It is, however, not only pores that are lacking, but also 

 a plated apical integument, as may readily be proved by dissection or 

 grinding either from above or from below, and by thin transverse 

 sections (see further, W. K. Spencer, 1904, Proc. Roy. Soc, vol. 74, 

 p. 43, 1. 9, where for 'ventral' read ' dorsal ' ; also Foerste, 1914, 

 op. cit., p. 409, § 13). Not that the absence of calcification would be 

 the smallest bar to sucker-action, or to locomotion, 1 but it suggests 

 that the animal rarely if ever relinquished its attachment. 



The lobes of the flexible integument round the apical pole have 

 been discussed more than once (Study II, 1900, p. 201 ; Study IV, 



1914, p. 169). They have been found in all specimens of Edrioaster 

 available for the prolonged preparation usually required; but this 

 area is obscured in Zebetodiscus, and in Dinocystis all that can be 

 traced is an occasional suggestion of an evagination (see text-fig. on 

 p. 135, vol. 6, 1899) and foldings indicative of a stretched membrane 

 (Study I, 1898, p. 546). 



The number of lobes is five in the holotype of Edrioaster buchianus. 

 In the specimens of E. bigsbyi the lobation is not so regular, but 

 there are indications of the same pentamerism. Within the rounded 

 margins of the lobes the integument is depressed, that is to say, 

 withdrawn towards the interior of the theca. The lobes in 

 E. buchianus were described as interradial, but in a form where 

 the subvective grooves coil round from one radius into another, 

 it is very difficult to decide upon the correct orientation of the 

 apical face. 



Whatever these lobes may mean, it is interesting to observe 

 precisely similar structures, apparently with similar interradial 

 position, figured by Jaekel in his Thecocystis sacculus (1899, pi. i, 

 fig. 1 b) and described as an " Ansatzflache " or " Anwachsungsflache". 

 In Stromatocystis also there is a pentagonal swelling with central 

 depression round the apical pole, but the angles of the pentagon are 

 prolonged in a distinctly radial direction. 



This evagination may have had something to do with temporary 

 fixation, but it does not reach as low down as the thecal periphery, 

 and this function does not explain its quinquelobate structure. The 

 only conclusions that can safely be drawn from the facts are that the 

 shape indicates some rather firm internal organ or organs with 

 quinque-radiate plan but without calcified skeleton. Beyond this 

 all is pure speculation. 



1 Cf. G. H. Parker, "The Locomotion of Actinians " : Science, March 26, 



1915, p. 471. 



