SPONGES.-HALLMANN. 



i8i 



may arise. These latter are, in all the observed instances, 

 simply digitiform, and they quite frequently become united 

 above with the main body. The consistency in alcohol is Hrni 

 and tough, and in the dry state rather hard and stiff. In some 

 specimens preserved in alcohol, the colour throughout is 

 purplish red; in others the dermal membrane is milky white, 

 the internal parts light brownish }ellow. In dry specimens, 

 as far as known, the colour, except of the dermal incrustation, 

 varies from straw yellow or rusty brown ; the darker hue be- 

 longs to those in which probably the life-colour was purplish, 

 although the type-specimen of T. rubens var. lamella, con- 

 trary to the implication of the specific name, shows no trace 

 either of red or brown. The sponge grows to a considerable 

 size. The largest specimen measures 265 mm. in height and 

 380 n in breadth. The thick- 

 ness of the lamella, and of 

 branches perpendicular to the 

 plane of growth, varies in 

 different specimens or in differ- 

 ent parts of a single specimen 

 from 5 to 10 mm. 



The main skeleton is a com- 

 pact reticulation of stronglv 

 developed horny fibre which, 

 even in the distal portions of 

 the sponge, frequently attains 

 a thickness of 160-200 ;/. The 

 pattern of the reticulation is 

 subject to a considerable 

 amount of variation, and the 



same is true with regard to the development of the spi- 

 cular core and to the size of the smooth megascleres. 

 As a matter of fact, the type-specimen of T. rubens var. 

 lamella departs to such an extent, in all three respects, 

 from the normal, that some hesitation was at first felt in identi- 

 fying it with the typical form. As a rule, the reticulation is 

 distinguished by a marked regularity, so that, in section, to 

 the naked eye, it appears quite rectangular. Under the micro- 

 scope, however, owing to the comparatively small size of the 

 mesh in relation to the thickness of the fibres, the apertures of 

 the reticulation are slightly rounded to sub-circular. In 

 vertical transverse section of a lamella or median longitudinal 

 section of a branch, the main fibres gradually trend outwards 

 to the surface on either side of the middle line in a pinnate 

 manner, dichotomosing repeatedly. The transverse fibres 

 connecting these are often further united by secondary connec- 

 tives parallel to the main fibres. Towards the surface these 

 secondary connecting fibres frequently become continuous and' 



Fig. 36a. A', pan ispinus. 

 Acanthostyli. b Chela. 

 Toxa. 



