68 



GEODIA VARIOSPICULOSA. 



tively and, to a smaller degree, also absolutely longer in the smaller var. inter- 

 media than in the larger var. micraster. The clades of the larger anatriaenes are 

 longest and the clade-rhabdome angles smallest in the small typical Geoclia 

 variospiciilosa; the former are smaller and the latter larger in the larger var. 

 intermedia, and the former still smaller and the latter still larger in the still 

 larger var. micraster. On comparing the figures 23-26 and 28-31 on Plate 17, 

 with each other and with Thiele's figure (loc. cit. Plate 6, fig. 6e) the differences 

 in the appearance of the cladomes of the large anatriaenes caused by these 

 differences in the clade-length and clade-rhabdome angle will be noticed. The 

 minute dermal anaclades of the smaller var. intermedia are larger than those of 

 the larger var. micraster. The size of the choanosomal oxyasters of the typical 

 Geodia variospiculosa and the two varieties intermedia and micraster is, like the 

 length of the clades of the large anatriaenes, in inverse proportion to the size of 

 the specimen in which they occur. Besides these differences there are others, 

 in the structure of the surface, the size of the pores, the relative frequency 

 of monactine asters and anatriaene-cladomes with stunted, rudimentary clades, 

 etc. 



Some of these differences, but hardly all of them, may be due to differences 

 in the forces acting on the different individuals. In particular I should say that 

 the differing ]3cculiarities in the shape and size of the cladomes of the large 

 anatriaenes and in the size of the oxyasters, should be considered as germinal 

 and therefore systematically important. The reason why these differences of 

 the anatriaenes and oxyasters should be considered as due to germinal peculi- 

 arities are : in the tetraxon sponges studied in this respect * the anatriaenes 

 of young (small) specimens have not only shorter clades but also larger clade- 

 rhabdome angles than those of older (larger) specimens, the clade-length increas- 

 ing and the clade-rhabdome angle decreasing with the age of the sponge. In 

 the sponges here under discussion, inversely, the clade-length decreases and the 

 clade-rhabdome angle increases with the size of the sponge. The size of the 

 oxyasters is in these sponges in inverse, the size of the sterrasters in true propor- 

 tion to the size of the specimens. The former lie in the interior of the sponge 

 and must therefore be less influenced by external forces than the latter which 

 lie near the surface. Differences of the internal oxyasters, not also seen in the 

 external sterrasters, cannot therefore, in my opinion, be ascribed to differences 

 of the forces acting on the growing sponge. This view is further supported by 



' For instance in Cinachyra vertex, sec R. v. Lendcnfeld, Tetraxonia. Ergeb. Deutsche SiUlpo- 

 lar-Expedition, 1901-1903, 1907, 9, p. 318. 



