REPORT ON THE KERATOBA. If 



negative, and on grounds of exactly the same nature as those forbidding the subdivision 

 of the Keratosa into Ceratina and Psammonemata, Carter, or Aplysinae and Sponginas, 

 Hyatt. There is a striking difference between the canal system of Aplysilla and Aiolysina. 

 The flagellated chambers of the representatives of the genera Aplysina and Verongia 

 (PL X. fig. 7) are small, pear-shaped, or rather hemispherical, each provided with one (1)^ 

 inhalent and one exhalent narrow canaliculus; and again, the surrounding ground-mass 

 is so very rich in granules that the outlines of the cellular elements in the neighbourhood 

 of the flagellated chambers are scarcely distinguishable. On the other hand, the flagel- 

 lated chambers of an Aplysilla or Icmthella (PI. II. figs. 4 and 5) are large and either of 

 regularly elongated form (pouch-shaped) or of quite irregular outline ; no special cameral 

 canaliculi are to be discerned; the flagellated chambers receive the water from the sub- 

 dermal cavities by means of numerous pores in. their walls, and expel it by means of 

 a large exhalent aperture ; the surrounding ground-mass is clear and transparent. There 

 are, however, amongst the horny sponges forms uniting these two extreme differences in 

 every direction. As to the size of the flagellated chambers, in Aplysina or Verongia it is 

 0"02 mm. on an average, in Euspongia or Cacospongia 0"026 mm., in Fhyllospongia 0'037 

 mm., in Carteriospongia 0"05 mm., in Spongelia 0'08 mm.; finally, in Aplysilla or 

 lanthella the flagellated chambers are still larger, reaching occasionally 0'15 mm. in length 

 by 0*05 mm. and more in width ; and it must be noticed — and this is very important — that 

 in some Spongelidaa (comp. PI. III. fig. 6) the fltigellated chambers are again very small, 

 their dimensions not exceeding those of the flagellated chambers of a typical Euspongia. 

 Further, as to their form, we have a thoroughly similar series of connecting links. In 

 the Aplysinidge they are either pear-shaped or rather hemispherical, in the Spongidse 

 typically hemispherical, in the Spongellidse more or less roundish, in the Darwinellidse 

 elongated. The same is also the case with respect to the presence or absence of special 

 cameral canaliculi. While in Aplysinidse each flagellated chamber possesses but one 

 exhalent, and probably also but one inhalent, canaliculus, these canaliculi being compara- 

 tively long and narrow, in the Spongidse they are short and broad, the inhalent system 

 of each flagellated chamber being besides represented not by one but by three, four, or 

 five canals, which sometimes are so very short that in many cases they can scarcely be 

 properly regarded as special differentiations of the corresponding subdermal cavities. 

 I refer the jeader in this connection to the drawing of F. E. Schulze^ and to my own 

 drawing on PL V. fig. 3, and wish to add that in many, indeed exceptional but still 

 numerous, instances I found in true Spongidai the flagellated chambers devoid of 

 any special exhalent canals, but just as is the case with the genus Carteiiospongia 



1 This question F. E. Schulze {Zeitschr. f. iviss. ZooL, Bd. xxx. p. 398) leaves undecided. I also was unable to come 

 to a decisive result with respect to Aplysina and Verongia owing to the inconvenience of these forms for certain manipu- 

 lations, but so far in this respect as analogous forms like Corticium, Chondrosia, and Chondrilla are concerned, there can be 

 no doubt that each iiagellated chamber possesses but one inhalent canaliculus. 



2 Zeitschr. f. loiss. ZooL, Bd. xxxii. pi. .xxxvi. figs. 11, 12. 



(ZOOL. CHALL. EXP. — PART Xi'XI. — 1884.) Hh 3 



