STUDIES ON THE COMPARATIVE ANATOMY OP SPONGES. 197 



their parallelism with the dermal surface and become irregu- 

 larly scattered. In other respects the arrangement of the 

 skeleton follows the ordinary Ute plan. 



Utella. 

 In this genus, of which the type species is HaeckeFs 

 Sycandra hystrix (5), we find a very remarkable modification 

 of the Grrantia type of skeleton, for a layer of longitudinally 

 disposed oxeote spicules is developed in the gastral cortex, 

 instead of, as in Ute, in the dermal one. For a descrip- 

 tion and illustrations of Utella hystrix I must refer the 

 reader to HaeckePs great work (6). 



Anamixilla. 

 Here, again, the skeleton is very peculiar, as will be seen at 

 once on referring to Polejaeff'^s drawing thereof (8). The 

 fiagellated chambers are elongated and radially arranged. The 

 gastral and dermal cortex, each with its skeleton, is developed 

 as in Grantia. There is, however, no articulate tubar 

 skeleton, although it is important to notice that subgastral 

 sagittal triradiates are still present, as in Ute argentea. 

 The most remarkable feature of this sponge is the presence, in 

 the chamber layer of the wall, of a number of large triradiate 

 spicules, out of all proportion to the size of the chambers and 

 arranged without regard to the direction of these, but generally 

 lying across them and more or less parallel to the dermal 

 surface. It looks as if the chamber layer had first lost the 

 greater part of its own skeleton, all except the subgastral 

 sagittal triradiates, and had then been invaded by large spicules 

 from the dermal cortex. 



Sycyssa. 

 In this very remarkable genus, for our knowledge of which we 

 are entirely indebted to Haeckel (5), the canal system appears 

 to be arranged upon the regular Grantia plan, but we are 

 told that the skeleton is made up solely of oxeote spicules, 

 there being no radiate spicules present of any kind. The 

 skeleton of the gastral cortex consists of (1) a gastral layer of 



