44 



seen in section , no longer supported on the tops of the collars, 

 which have been retracted , drawing the membrane after them 

 close down into the apices of the cells. So Sollas's membrane 

 remains visible even when the collars of the cells are retracted, 

 which indicates that it is probably a more or less permanent 

 structure, and no mere temporary fusion of the margins of adja- 

 cent collars". 



1891. Dendy Arthur, Studies on the Comparative Anatomy of 



Sponges. IV. On the Flagellated Chambers and Ova of 



Halichondria panicea. In : — Quart. Journ. Mier. Sc. (2) Vol. 



XXXII p. 41—48; PI. V. Vide pp. 42—47. 



»I find in this sponge the best example with which I have 



yet met of Sollas's membrane We now come to the most 



important consideration , viz. the form and arrangement of the 

 collared cells; and we will first describe them as they appear 

 when the chamber is seen in section .... The collared cells stand 

 some little distance apart from one another on the gelatinous 

 ground-substance surroundiug the chamber. They have each a 

 short nucleated body, indistinguishably from the collum or neck, 

 and surmounted by the delicate funnel-shaped coUar. The out- 

 lines of the collars are extremely fine, but all the collars are 

 connected at their margins by a very distiuct membrane , which 

 appears in section as a thicker line running from one to the 

 other, but interrupted by the mouths of the collars, as shown 

 in the figure. The structure and relations of this membrane 

 (Sollas's membrane) appear exactly as I have described them in 

 Stelospongos (sic). The collared cells nearest to the exhalaut opening 

 of the chamber are shorter than those farther away , so that the 

 membrane gradually approaches more and more closely to the 

 gelatinous groundsubstance around the chamber, and finally seems 

 to run into it at the opening itself. .... The fact that Sollas's 

 membrane appears here as a thicker line than the outlines of the 

 collars is , I believe , simply due to the thickness of the sections 

 causing us to see a little more than the mere cut edge of the 

 membrane Flagella were seen, »projecting from the bodies 



