490 BULLETIN 100, UNITED STATES NATIONAL MUSEUM. 



fibers of the Albatross sponge and Keller's type would have to be 

 looked on as a ease of analogical resemblance. We should have to 

 conclude, in other words, that both in A ply sill a and Aplysina cer- 

 tain offshoots had developed the morphogenetic habit of not secret- 

 ing a firm spongin layer on the outside of the fibers; In case all 

 this, which seems very unlikely, should turn out to be so, the 

 Albatross sponge should be received into a new genus close to 

 Aplysina. The character of the fibers is so peculiar as to deserve 

 generic value, although the sponge is obviously related to Aplysina, 

 and Pendrosponyiu. 



Schulze, 1878 (p. 401), first pointed out that the medulla of the 

 Aplysina fiber is finely reticular in structure. He notes also (p. 399) 

 that in young fibers the spongin wall may be only one-thirtieth to 

 one-tenth total diameter of the fiber, although it increases not only 

 in absolute but in relative thickness as the whole fiber grows thicker. 

 In Aplysilla he finds (1878. p. 411) that the finer structure of the 

 fibers is essentially as in Aplysina. Lendent'eld (1889, p. 398) says 

 that the pith in the Aplysina fiber shows a reticulate structure. 

 He records species (p. 416) in which the pith forms nine-tenth of 

 the thickness of the fiber, the surrounding spongin forming only a 

 very thin, although laminated, coating. In Porto Rican specimens of 

 Aplysina fiagelliformis anomala and Dendrosponyia crassa I find 

 that the pith is composed of a minutely reticulated substance. The 

 pith of these fibers or the pitli plus the very innermost spongin 

 evidently corresponds to the whole fiber of Psammaplysilla. 



Another sponge must be considered in this connection. This is 

 Aplysina purpurea, first described by Carter, in 1880, from Ceylon, 

 and later (18816, p. 103) more fully described by him, the distribu- 

 tion being extended to Australia. Dendy (1889, p. 97; 1905, p. 224) 

 has studied Ceylon (Gulf of Manaar) specimens of this species. The 

 sponge is more or less conical or massive; conulated; may reach 195 

 nun. in height. The skeleton is composed of dense local aggregations 

 of very irregular, branching and anastomosing horny fibers accumu- 

 lated along certain tracts to form the so-called compound fibers, while 

 large intervening areas remain free from fiber altogether. The fi- 

 bers themselves have a very curious structure, consisting of a very 

 thin outer layer (if any) and a very- thick pith, the latter exhibit- 

 ing a granular or often minutely reticulate appearance. They are 

 free from foreign bodies (Dendy 1905). Dendy concludes that 

 Keller's I'siiiiinidplysUla arabica is very closely related to, if not 

 identical with, ^4. purpurea. Carter (18816) says that in A. pur- 

 purea the ectosome (dermal sarcode) is fibrous below, with abund- 

 ant pigment cells. The color in alcohol is black purple. What Car- 

 ter terms horn cells (18816, pi. 9, fig. l,e) aiv doubtless, as he con- 



