MATERIALS FOR A MONOGRAPH OF THE ASCONS. 533 



a species from Yillafranca which he termed Nardoa spon- 

 giosa.^ Kdlliker discovered the spicule sheath left behind 

 after the spicule is dissolved by acetic acid. On the rays of 

 the quadriradiates which project into the gastral cavity the 

 author observed " another problematic structure, namely, a 

 dark, granulated, conical mass, which envelops the calcareous 

 ray, and also, as it seemed to me, the sheath. Seen in surface 

 view these structures appear as round cells, and only profile 

 views make clear their true relations (pi. vii, fig. 10). In 

 some cases this dark granular mass is continued in reduced 

 quantity (verschmalert) over the portion of the calcareous ray 

 lodged in the epithelium ; but I was unfortunately unsuccessful 

 in discovering the true significance of this curious structure" 

 (p. 65). It is easy to recognise in this account a description, 

 perfectly accurate as far as it goes, of the cells I have termed 

 the gastral actinoblasts, the secreting cells of the gastral rays. 

 The cells which the author mentions further on in his descrip- 

 tion as occurring on the walls of the canals near the ciliated 

 epithelium, " rather larger rounded cells, singly or in groups, 

 the significance of which remained unknown to me^^ (p. 65), 

 were very probably porocytes. 



' Haeckel identifies Kolliker's "Nardoa spongiosa" with either 

 "Ascaltis Gegenbauri" or cerebrum. lam inclined to dispute both 

 these identifications for the following reasons : — (1) Haeckel's "Ascaltis 

 Gegenbauri" is figured by him as having the gastral layer folded like 

 Ascandra falcata; this is a point which certainly would not have escaped 

 KoUiker, who neither mentions nor figures any such peculiarity; (2) the 

 excellent figures of the sponge given by KoUiker (pi. ix, figs. 6, 7) are 

 not from a specimen of Clathrina cerebrum; (3) there is a distinct 

 reference on p. 54 of KoUiker to monaxons in his sponge, though he does not 

 mention them in the special description. From Kolliker's figures of the 

 sponge and of its long and slender gastral rays (pi. vii, fig. 10 ; and pi. ix, 

 fig. 8) I am inclined to identify it as contort a, which is one of the com- 

 monest Ascons in the Gulf of Lyons ; or possibly as spinosa, Lendenfeld, 

 which, as I have stated above, 1 believe to be identical with contorta, 

 differing only in the total absence of the monaxon spicules so variable in size 

 and number in the true contorta. The gastral ray figured at pi. vii, fig. 10, 

 is not full-grown, as shown by the position of the actinoblast near the base. 



As KoUiker had ten specimens of his sponge there may possibly liave been 

 more than one species amongst them. 



VOL. 40, PART 4. NEW SER. P P 



