108 PORIFERA. III. 



opening; I have not seen pore-sieves but the papillae with the large opening are in all probability 

 pore-papillae, the others being oscular papillae, the facts being thus as in H. verrucosa, 



The skeleton. The dermal skeleton; the skeleton formed by the dermal spicules is by far the 

 most developed and it occupies nearly the whole body of the sponge; it consists of fibres which 

 stretch from the main skeleton or quite from the base and obliquely towards the surface, but they run 

 generally so obliquely, that they are for long distances more or less parallel with the surface, and the 

 skeleton is on the whole rather irregular on account of the manner in which the sponge grows; the 

 fibres are somewhat numerous and they are also rather strong, of a thickness up to 0-12 mm . The 

 fibres stretch horizontally just below the dermal membrane and terminate in it, but there are no 

 spicules proper to the membrane. The fibres lying below the membrane run together at the base of 

 the oscular and pore-cones and continue up in the wall of these, forming thus a skeleton which consists 

 of densely placed parallel spicules with the ends towards the opening of the cone. The main skeleton 

 is somewhat weakly developed and consists as usual of acanthostyli with the heads based on the sub- 

 stratum, but the styli are much scattered and not numerous. At the heads of the acanthostyli there 

 is a very small amount of spongin. 



Spicula: a. Megasclera. i. The skeletal spicules are acanthostyli which are divided into 

 two well separated groups, large and small. The large styli are straight or slightly curved, the head 

 is small or not at all developed; they taper evenly outwards but at the end they are abruptly pointed 

 with a short point; they are spined only on the basal part at most in the lower half part; most of 

 the spines, especially those on the head, are somewhat strong. The length is 0-30 0-417 ram and the 

 diameter of the head 0-018 0-022 mm . The small styli are straight and spined in the whole length, but 

 the spines are small and scattered in the outer part, otherwise they are relatively robust; these styli 

 are somewhat uniform in size, the length being 0-107 0-13 ram and the diameter of the head 0-014 

 0-019 mm . 2. The dermal spicules are long and straight strongyla with one end thicker than the 

 other; they may be slightly polytylote; the ends may sometimes be very slightly swollen, especially in the 

 thinner strongyla. The length is 0-33 0-45 mm and the diameter 0-006 o - oio mm . Microsclera are not present. 



This species is interesting in a certain respect; it resembles to a very high degree one of the 

 species with chelae, viz. H. stylata; the only differences, besides the want of the chelae, are that both 

 the styli and the dermal spicules are slightly smaller in the present species than in stylata, but this 

 is of no specific value; otherwise the growth, the surface with its papillae, the structure of the dermal 

 membrane, the arrangement of the skeleton and the shape of both kinds of spicules agree very well in 

 the two species, and if it were not for the difference in the possession and non-possession of chelae, 

 and the difference in the structure of the dermal membrane, to which the want of the chelse seems 

 to give rise, I should not hesitate in uniting them. As however I have otherwise never found, that 

 the same species may be with or without chelae, I think it necessary to consider the present species 

 as specifically distinct from H. stylata.' 1 } It is to be remarked, that the specimens of both species are 



') To be sure Topsent has described (Resultats du Voy. du S. Y. Belgica, Spongiaires, 1901, 18.) a species without 

 sigmata as Lissodendoryx spongiosa R. and D. var. asigmata, and in the same place the author strongly advocates the view that 

 sponge-species are capable of varying in such a way, that they may want a form of microsclera otherwise present in the 

 species; I cannot at all agree with Topsent in this view, and with regard to the examples he mentions (Hamacantha John- 

 soni, Desmacella Peachii) I have proved (The Ingolf Exp. VI, I. 1902) that the supposed varieties are distinct species, and with 

 regard to H. Johnsom Topsent has himself in his work from 1904 admitted the specific validity of his former varieties. 



