42 ARTHUR DENDY. 



stained with borax carmine, and cut by the ordinary paraffin 

 method. 



I at one time hoped to be able to publish a complete account 

 of the minute anatomy of Halichondria panicea; but my 

 removal from England and the pressure of other work render 

 this impracticable, and I must content myself with describing 

 only the most important points. This is particularly de- 

 sirable, because I find in this sponge the best example with 

 which I have yet met of Sollas's membrane, the very existence 

 of which has lately been called in question by Dr. R. von 

 Lendenfeld.^ I need not here reply to the arguments of this 

 observer, because I have already done so in my article on 

 " Some Old and New Questions concerning Sponges,^' in the 

 ' Zoologischer Anzeiger,^ ^ and more fully in the third of 

 my " Studies on the Comparative Anatomy of Sponges," re- 

 cently sent to England for publication in the ' Quarterly 

 Journal of Microscopical Science.' To these papers and to 

 the second of my " studies,^' already cited, I must refer the 

 reader for further information, and for the literature of the 

 subject. 



Halichondria panicea may be so readily obtained in 

 England, that any student of sponges acquainted with the 

 modern method of research can easily satisfy himself as to the 

 correctness of the observations here recorded. 



Before describing the flagellated chambers of Hali- 

 chondria panicea it will be advisable to say a few words as 

 to the canal system. This is of the lacunar type. The inhalant 

 pores, scattered over the surface of the sponge, lead into a 

 system of irregular lacunae, scarcely definite enough to deserve 

 the name of canals. The ectosome is thin, and the subdermal 

 cavities are not recognisable as distinct structures. As they 

 penetrate below the surface, branching again and again, the in- 

 halant lacunae become smaller and smaller, being recognisable 

 in sections only as minute cavities surrounded by the flagel- 

 lated chambers. Interdigitating with the inhalant lacunae in 



^ ' Zoologisclier Auzeiger,' No. 311, 1889, p. 3G2, 

 2 No. 325, 1890. 



