REPORT ON THE KERATOSA. 5 



flagellated chambers, each possessing its own narrow inhalent and exhalent canaliculi, 

 and while the ground-mass surrounding these flagellated chambers is always opaque 

 owing to the presence of small granules, the forms like Spongelia and Aijlysilla possess 

 no special cameral canaliculi, their large pouch-shaped flagellated chambers receiving the 

 water from the subdermal cavities directly by means of the pores in their walls, and 

 expelling it also immediately, without the help of any intermediate narrow canals, 

 into large exhalent cavities, the diameter of these latter being usually far larger than 

 that of the exhalent opening of the corresponding flagellated chambers ; and that in 

 these latter instances the parenchyma in the zone of the flagellated chambers is devoid 

 of any granules, being lucid and transparent. 



It remains to be decided what position the modern systematist should take with 



respect to the antagonism in question. F. E. Schulze himself gives in his papers 



no answer to it. He assigns^ to Aplysilla the place of a new genus in his family 



Aplysinidse, while he is inclined to regard the genus Spongelia, an analogue of 



Aplysilla in the Keratosa with homogeneous skeletal fibres, as the representative 



of an independent family.^ Again, his distinguished pupil Dr. Vosmaer, stands also 



perfectly neutral, dividing, in his interesting paper on Velinea gracilis,^ all the 



Keratosa directly into families, according to the properties both of the soft parts and of 



the skeleton. But though neutral as far as his actions are concerned. Dr. Vosmaer 



expresses very clearly his opinion on the matter. He does not ascribe any special 



importance to the diff"erence between the fibres, whether homogeneous or heterogeneous. 



On the contrary, another pupil of Prof. Schulze, Dr. v. Lendenfeld, seems inclined to 



accept the opinions of Hyatt and Carter. At least, in his memoir on the Aplysinidae of 



the South Sea, he characterises^ the family of Apl3'sinid£B by their heterogeneous 



skeletal fibres, splitting it into two subfamilies, that of Aplysininae and Aplysillinae, 



according to the type of the canal system. And, indeed, such a proceeding appears at 



first sight very logical and natural. Of course, on the whole, the canal system is of 



greater significance for the sponge organism than ■ the skeleton. No sponge can be 



imagined without canal system, be it represented as in Asconidaj by the undifferentiated 



central cavity without any trace of separate flagellated chambers, or, as in Ap>lysina or 



Corticium, by a very complicated system of subdermal cavities, inhalent cameral 



canaliculi, flagellated chambers, exhalent canaliculi, &c., while there are sponges, like 



Halisarca, Oscarella, or Chondrosia without any supporting apparatus. It should 



not, however, be overlooked that whatever importance may be ascribed to the canal 



system, this importance is of a pronounced physiological character. On the contrary, 



so far as the properties of the skeleton are concerned, — all this holds true within 



the group Keratosa, and the last-mentioned point with regard to its internal 



1 Zeitschr.f. iviss. Zool., Bd. xxx. p. 404. ° Zeitschr.f. wiss. Zool., Bd. xxxii. p. 117. 



' Mittheilungen a. d. zool. Station zu Neapel, 1883, p. 444. * Zeitschr.f. loiss. Zool, Bd. xxxviii. p. 309. 



