APPENDIX — SPONGES OF THE "ABGO" CRUISE. 221 



Also the gland-cells are not restricted to a special part of 

 the mesoderm, but they are most numerous in the dermal 

 membrane, just beneath the ectoderm. They are large, 

 round, granular, with a small nucleus, and were often 

 seen to project with a small pointed prominence (the 

 mouth) beyond the ectoderm. They contain a varying 

 amount ol red pigment and seem to fulfil the double 

 function of gland cells and pigment cells. In my former 

 paper I described these cells only as pigment cells. 



According to Lendenfeld two species of Aplysilla have 

 been described as British: A. sulpliiirea, Schulze, 

 found off the Shetland Islands; and A. rosea, Schulze, 

 which Lendenfeld regards as identical with Aplysina 

 ncevus, Carter, dredged on the "Porcupine" expedition, 

 1869, between Scotland and Faroe Islands (345 fathoms) 

 and north-west of the Shetland Islands (312 fathoms) . A . 

 sulphurea of course differs from my species in its colour. 

 A . rosea comes much nearer to it, but it is very difficult 

 to get a correct idea of the degree of its relationship with 

 A. rubra, since, as far as I know, no sections of it have 

 been figured. Carter gives only the figure of a spirit - 

 specimen, Lendenfeld even only a figure of a dried 

 specimen. However, as Lendenfeld states that in A, 

 rosea " the pigment occurs in the shape of large red 

 spherical granules which are found in the amoeboid and 

 collar cells," we may take this as distinguishing it from 

 A. 7'iibra, which contains no pigment in those cells, but 

 only in the gland-cells. 



