REPORT ON THE KERATOSA. 31 



number and quality tlius characteristic of every sponge and not dependent on the 

 peculiarities of the surrounding soil, it would still be practically impossible to 

 distinguish Cacospongia from Oligoceras by these characters alone. And the 

 third additional character of the latter would be also of very little assistance. 

 The skeleton of Cacospongia is represented by a continuous network of fibres ; that 

 of Oligoceras is interrupted by spaces of parenchyma devoid of any skeleton, so 

 that, on the whole, its chief fibres show a tendency to free themselves, to separate 

 from one another in order as is the case with Aplysilla, and to form tree-like forma- 

 tions. But this character, or rather tendency, is common to all Spongidre with 

 skeletal fibres overcharged with foreign enclosures ; in my Cacospiongia spinifera and 

 Cacospongia tuberculata, amongst fibres forming obviously a continuous network, I find 

 fibres whose secondary ramifications do not reach the neighbouring primary fibres, so that 

 a small tree is actually formed. In Spongelia spinifera F. E. Schulze^ found a form with 

 a still more pronounced tendency in its skeletal fibres to ramify, to lose connection with 

 one another in order to form small tree-like structures. He did not, however, create 

 for it a special genus. Again, as before alluded to, the conjectural generic characters 

 of Oligoceras seem to be of a very unstable nature, and this is the second ground why 

 the genus Oligoceras should not be adopted even provisionally. 



The genus Halisp)ongia, Bowerbank, being according to 0. Schmidt identical with 

 his Cacospongia, the genus Ditela, 0. Schmidt, having been given up by Schmidt himself, 

 who pointed also to the necessity of the same proceeding with respect to the genus 

 Auliscia, Bowerbank, there remain only the genera Hircinia and Ceratella to be 

 mentioned, since the names Stematumenia, Bowerbank, Polytherses, Fonbressin and 

 Michelotti, and Filifera, Lieberkiihn, are synonyms of Hircinia. The subgenus 

 Sarcotragus, established by 0. Schmidt in the year 18G2, was abandoned by him in the 

 following year. 



As to the genus Hircinia, the reasons why I cannot adopt the family Hircinidse 

 in the sense of F. E. Schulze and Vosmaer have been stated in the foregoing pages 

 (pp. 12-14), and indeed the grounds above mentioned which forbid us to use the 

 presence of parasites in order to characterise the family, also forbid the use of this 

 character for purposes of generic distinction. It is not without interest that amongst 

 the Challenger specimens I have forms attached by filaments, some of which, according 

 to their other properties, I must group in the genus Stelospongos, others in the genus 

 Oligoceras, had it been retained, and others in the genus Cacosp)ongia. Should we 

 adopt the name Hircinia for forms with very large meshes and with fibres overcharged 

 with foreign enclosures as Carter and Hyatt have done ? I think this would be a very 

 doubtful proceeding ; the above characters are also common to Oligoceras, and we have 



1 Zdtschr.f. wiss. Zool., Bd. xxxii. p. 152. 



