These statements were confirmed by Lendenfeld (1894 r) p. 115): "die Geodia-Sterraster gehen 

 aus kleinen Stechapfelförmigen Kugeln mit zahlreichen, ungemein feinen, streng konzentrischen 

 und unter einander gleich grossen Strahlen hervor; wahrend die Jugendstadien der Placospongia- 

 Sterraster crekrümmte, dornige Stiibe sind. Demnach ware der Geodia-Sterraster als eine polyaxone, 

 der Placospongia-Sterraster aber als eine monaxone Nadel aufzufassen." 



Hanitsch described (1895 p. 214 — 216) a new sponge, Physcaphora decorticans. Here 

 he found "a new type of microscleres" for which he proposed the name "selenasters." These 

 spicules corresponcl in position, according to the author, to the sterrasters of Geodidae. There 

 are however fundamental differences. "In the youngest condition present the spicules had the 



shape of rods, nearly straight or slightly twisted, beset with minute spines In the next 



stage the spicule is still pretty straight, but the spines are large and numerous, although still 



distinctly separated In the next stage, the spicule has already its typical sausage-shape, 



the spines are very closely set, but still recognisable in their individuality The last stage 



is the full-grown selenaster, in which the spines, except their most distal ends, are all fused so 



as to form one solid mass The distal ends of the spines project a short distance beyond 



the surface of the spicule, and being polygonal, chiefly hexagonal in transverse section, offer 

 a delicate pattern, when the spicule is being focussed at different depths. A hilus is present 

 as in the Sterrasters. We thus see a great resemblance in the structure and development of 

 Sterrasters and Selenasters. The chief difference is that in the Sterrasters all rays start from a 

 point, whilst in the Selenasters the rays start from a line." From this description, which is 

 accompanied by several figures it becomes evident that the selenasters of Hanitsch are the 

 sarne sort of spicules as the sterrasters of Placospongia described by Keller and Lendenfeld. 

 Moreover, we shall see that Thiele (1900 p. 72) was right in identifying Physcaphora with 

 Placospongia. 



Unaware of the paper of Hanitsch, Lendenfeld (1897 p. 51) called the spiculum under 

 consideration "pseudosterraster." As the two names may easily create confusion, because the 

 spicula are monaxons and not polyaxons, we prefer to use the new name, sterrospira, 

 proposed by one of us (Vosmaer, 1902 p. 111). A detailed description and a few illustrations 

 of the development of these sterrospirae are finally given by Lindgren (1898 p. 362 — 364: 

 PI. 18, fig. 21 — 22). This author likewise was not acquainted with the paper of Hanitsch nor 

 with that of Lendenfeld (1897). He is, therefore, wrong in supposing that neither a description 

 nor sufficiënt illustrations existed concerning the sterrospira. 



The observations of previous authors agree in the main points, and on the whole 

 we can but confirm them. It is, therefore, superfluous to give detailed descriptions ; our figures 

 better illustrate our observations and easily show how far we agree with Keller, Hanitsch, 

 Lendenfeld and Lindgren. On PI. IV, fig. 5 a — £ we have illustrated the mode of development 

 for Placospongia melobesioides \ in fig. 9/. — 7, and on PI. V, fig. 1 y. — 5 the same for P. carinata. 

 For these two species there is neither in the mode of development, nor in the final result any 

 marked difference. True, neither the early stages, nor the adult ones are always absolutely the 

 same. But the differences are not bound to one species or the other. In the early stages 

 differences are seen e. g. in the way of spinulation. If we compare fig. 1 u. on PI. V with fig. 5 a 



