CRATEROMORPHA MEYERT. 63 



Tho hypodermnlia are mainly oxypontactins of a comparative- 

 ly large size and with latlier strong rays. The paratangentials 

 may he 1.") mm. long and the unpaired proximal ray, 2.5 mm. 

 The rays at l)ase may attain a thickness of 100 //. 'J he pointed 

 ends of rays usually show no roughness of surface. There occa- 

 sionally occur exceptionally small and thin-rayed oxypentactins, 

 situated somewhat deeper than those of more normal size ; they 

 ]irobal)ly represent early stages in the development of the hypo- 

 dermalia. The meshwork formed l)y the paratangential crosses is 

 irregular (PI. IV., fig. 6). 



In addition to the pentactinic hypodermalia there are ob- 

 served at intervals slender diactins, which, running either solitar- 

 ily or in small bundles, are in direct contact with the dermal 

 layer and so serve as its support. They are thus to be regarded 

 likewise as hypodermalia ; however, it must be said that as such 

 they play only a subordinate rôle in comparison with the pent- 

 actinic forms. In the Sei. Coll. specimen the diactinic hyj^oder- 

 malia are quite few and far l)etween ; in the larger specimen 

 Ijelonging to Mr. OwsTOX, they are somewhat more numerous. 

 It may be that as the sponge increases in size, their number is 

 more or less augmented by transference from the ranks of the 

 parenchymalia. It will later lie seen that in large specimens of 

 both the subsjiecies iuberosa and rf/gosa, the numerical ratio of 

 pentactinic to diactinic hypodermalia is reversed, the latter 

 greatW predominating over the forjner in numl)ers. J>at it is of 

 course impossible to predict that the same will ultimately take 

 place also in the typical species after a great advance in growth. 



There exist in this species no spicules, which can be speci- 

 fied as the hypogastralia. 



