REPORT ON THE HEXACTINELLIDA. 271 



During 1875 and 1876, in his Monograph of the Silico-fibrous Sponges, parts iii.-vi.,^ 

 Bowerbank ascribed no fewer than fourteen new species to his genus Farrea. These 

 he names Farrea gassioti, Farrea pocillum, Farrea Jistulata, Farrea Isevis, Farrea 

 parasitica, Farrea valida, Farrea spinosissima, Farrea spinifera, Farrea spinulenta, 

 Farrea aculeata, Farrea rohusta, Farrea inermis, Farrea perarmata, and Farrea 

 irregularis. Since, however, the description of these new species was usually based 

 only on a small fragment without characteristic form, and withal more or less macerated 

 and injured, it is impossible, in most cases, to determine (notwithstanding the perfect 

 figures given under a magnifying power of 36 or 80 diameters) to which species 

 the fragment in question properly belongs. It is much to be regretted that, in 

 almost all these Bowerbankian species of Farrea, the free spicules of the dermal 

 system were not preserved or are not sufficiently clearly figured, and accordingly the 

 words used by Bowerbank at the close of the introduction to the monograph referred 

 to must be employed; he says: — "When the expansible dermal system is present, 

 wholly or in part, in specimens under examination, we are enabled to establish specific 

 characters of external form and structural peculiarities of the most satisfactory 

 description, but when that important portion of the organic structure of the sponge 

 is absent the characters derived from the form and surface of the rigid skeleton 

 are necessarily provisional, and can maintain their ^jlaces in its description only until 

 a specimen in a natural and perfect state can be procured." Since Bowerbank, 

 moreover, lays the very greatest weight on the width of the axial canals and regards 

 these — as his generic diagnoses "fibres canaliculated, canals continuous" indicate — as 

 at least essentially in a condition of perfect continuity, whereas, as Carter has already 

 observed, in the skeletal framework of the Hexactinellida, the axial canals of the 

 individual hexradiate spicules are at first unconnected, while the width depends chiefly 

 on the condition of the skeleton as regards maceration or solution, it is conceivable 

 that the specific characters and differential features given by Bowerbank have often 

 little value. 



The two types indicated by Bowerbank {loc. cit., p. 272) as Farrea gassioti, and 

 Farrea pocillum agree so thoroughly in form, size, and structure that it is really only 

 the different breadths of the central canal of the network of beams that form the 

 difference. But this distinction is seen to be insignificant when it is observed that, 

 even according to Bowerbank's own statement, some greatly macerated specimens of 

 Farrea gassioti have the central canals remarkably wide and clear. Further, in the 

 case of the two specimens of Farrea pocillum, which have the soft parts dried and 

 richly provided with the included isolated spicules, and which were accordingly, 

 without doubt, secured as fresh specimens, the canals are especially delicate, and in 

 some places even almost imperceptible. Moreover, the great similarity in form, size, 



' Froc. Zool. Soc. Lond., 1875, 1876. 



