284 Mr. H. J. Carter on 



skeletal fibre light brown, as will be seen by the following 

 description ; while, as I have before stated, in identical speci- 

 mens of what I now know to be Dendrilla rosea it may be 

 flesh-coloured and grey or colourless respectively. 



Aplysina massa. 



Massive, slightly lobate, sessile, contracted towards the 

 base. Colour mouse- or dark grey. Surface even, presenting 

 the usual dermal, soft, fibro-rcticulation raised into conical 

 points by the ends of the dermal filaments of the subjacent 

 keratose fibre. Pore-areas in the interstices of the reticula- 

 tion. Vents scattered here and there. Structure fleshy, 

 supported on keratose fibre. Fleshy part more or less can- 

 cellated by the canals of the excretoiy systems ; traversed 

 perpendicularly from the circumference by large inhalant 

 "fold-bearing " canals (that is, canals surfaced by transverse 

 folds or sharp ridges of the lining membrane, which, partially 

 encircling the canal in segments of a circle, thus intercross 

 each other's terminations longitudinally like the " valvulce con- 

 mventes^^ of the small intestine), which commence immediately 

 under the cribrilbrm pore-structure of the surface apparently 

 without the intervention of subdermal cavities ; hence the 

 situation of their mouths respectively may be seen from the 

 outside, as their dark circular areas loom through the cribri- 

 form structure : keratose fibre aplysinoid, of a light-brown 

 colour corresponding with that of the flesh ; consisting of 

 large and small filaments, the former arising singly in a plu- 

 rality of points and pursuing an unbranched, i. e. undivided, 

 course to their termination, in an attenuated form respectively 

 on the surface ; the latter branching off from the former, but 

 not by division of the central canal of the larger fibre, as will 

 now be explained. 



Having macerated a large portion of this specimen in water, 

 so as to rid the keratose skeleton of all soft parts, the skeletal 

 structure was placed between two jneces of glass, with suffi- 

 cient water to fill up all the vacuities, in which condition it 

 was examined under a low microscopic power, and the appa- 

 rent branches found to be not divisions of the large fibres, 

 but additions to their surfaces respectively, formed by the 

 development of the " horn-cells " of the sarcode thus applied 

 to them. 1 have already described and illustrated the " horn- 

 cell " and this mode of growth in Aplysina corneosteUata = 

 Darwinella (' Annals,' 1872, vol. x. p. 107, pi. vii, figs. 4 

 and 5), and in the present instance they were observed to be 

 in great plurality, attached to the outside of the larger fibres, 



