STUDIES ON THE COMPARATIVE ANATOMY OF SPONGES. 519 



The flagellated chambers are more or less elongated or pear- 

 shaped sacs, measuring about O05 mm. in length by 003 mm. in 

 transverse diameter. They are provided with narrow excurrent 

 and incurrent canaliculi as represented in the diagram, fig. 7. 

 The canaliculi are extremely difficult to make out, but I have 

 repeatedly examined a large number of sections, both trans- 

 verse and longitudinal, and have satisfied myself of their 

 existence. Their lumina, possibly owing to the contraction of 

 the Sponge in spirit, are especially obscure, being only very 

 occasionally discernible. They commonly appear as short, 

 slender cords, leading to the proximal or distal end of the 

 chamber, as the case may be, and are chiefly visible owing to 

 the presence around them of the minute refringent granules 

 already referred to. As usual in ordinary spirit specimens little 

 can be made out concerning the collared cells. They appear to 

 be very minute, and all I have succeeded in observing are their 

 small nuclei and a number of irregular, gelatinous-looking pro- 

 cesses projecting into the lumen of the chamber, and probably 

 representing the remains of the flagella. The exhalant canaliculi 

 unite together and open ultimately into the central oscular 

 tube, whence the stream of water is discharged through the 

 single osculum at the summit of the Sponge (fig. 2, o.). 



I have endeavoured to represent in fig. 7, in a purely diagram- 

 matic form, what I believe to be the relations of the flagellated 

 chambers to the exhalant and inhalant canaliculi. It thus 

 appears that the flagellated chambers are of the type described 

 by Sollas as " diplodal," although the inhalant canaliculi appear 

 to be but short. It is worthy of note that I have seen in one 

 instance a flagellated chamber apparently opening direct out of 

 a subcortical crypt without the intermediation of a canaliculus. 

 It is obvious that such an occurrence would be most likely to 

 take place, if anywhere, where the canal system is lacunar, and, 

 as already pointed out, the subcortical crypts are the only 

 portions of the canal system iu Ridleia oviformis which 

 are lacunar. 



