4§6 G. C. J. Vosmaer 



and L. cramhessa between 50 and 70 mm. Fig. 1 on Piate 28 is an 

 «individuai« of a colony measuring 210 mm. The specimen in fig. 2 was 

 still somewhat longer. 



The second point in Haeckel's diagnosis regards the apical ray of 

 the tetrasceles. Also this factor is by no means Constant as I often saw 

 long rays in flat specimens (PI. 29 fig. 3). Finally there is snpposed 

 to be a difference in the shape of the tri- and quadriradiates, being in 

 crambessa more regulär than in aspera. Nobody of course would con- 

 sider this alone of specific value and thus we may declare them all for 

 varieties of one species. It is too well known that an accurate anatomi- 

 ca! account, as we want it now, is not to be found in the »Monograph«. 

 I gave something of it in a previous paper on L. aspe^-a^^ and now only 

 have to add that the canal-system of all the varieties is identical in main 

 points. I will speak hereafter about some modifications. 



Having stated now that Leucoma aspera (0. S.) Vosm. shows a 

 polymorphosis as is hardly known in any other Calcareous Sponge^ it 

 will be of some interest to look out for its reason. The variety typica 

 is as a rule small, thick-walled and rough ; the variety gigantea is large, 

 rather thin-walled and smooth. Between these extremities there is a 

 variety crambessa which is characteristic by its flatness and its shape, 

 being ramified or lobed, often resembling very much a cocks-comb. But 

 there are very many transitions. Fig. 4 on Piate 28 shows a very flat 

 specimen which may be called gigantea^ although the typical variety of 

 that name (fig. 1 and 2) is not at all so fiat and about three times as big. 

 In fig. 1 the specimen has a rather even surface, in fig. 2 it is over- 

 loaded with cylindrical or conical protuberances. In fig. 5 these are flat, 

 and the Sponge-body itself is more or less elliptical (on sections). 

 In fig. 2 both are elliptical or circular. In how far the wideness of 

 the individuals of one colony vary may be seen in fig. 6. The varieties 

 typica and cramhessa live under circumstances that seem to be the same. 

 Both are fixed on stones : both live in a depth of about 1 meter. Why, 

 we ask of course, is one variety flat and rather smooth, the other thick 

 and rough? The big variety gigantea however is always found attached 

 to the keel of vessels. I consider this fact to be of great importance for 

 the Solution of our question. Sponges are all fixed animals. The only 

 way for them of providing themselves with the wanted nourishment is 



» Vosmaer, Über Leucandra aspera H. Tijdschr. Ned. Dierk. Ver. Bd. V. 

 p. 144—166. 



2 PoLÉJAEFF (Voyage of the Challenger. Vol. VIII. Part XXIV. Calcarea. 

 p. 54) described something of this sort in his Leucoma multiformis. 



