PORIFERA. II. 



35 



1875. Espcria lanugo O. Schmidt, ibid, fiir 1872 — 73, 118. 



1879. Espcria stohnifera Merejkowsky, Mem. de l'Acad. imp. des sc. de St. Petersb., Ser. 7, XXVI, Nr. 7, 



22, PL I, figs. 13, 14, PI. Ill, figs. 4, 5, 12—19 and 23—29. 

 1891. Chalinula ovulum Grentzenberg, Spongienfauna der Ostsee, Inaug. Dissert, Kiel 1891, 27, Fig. 13, 14. 

 1891. Esperclla lanugo Grentzenberg, ibid. 34, Fig. 22 — 26. 

 1893. Esperella ovulum Levinsen, Det vidensk. Udbytte af Kanonbaaden Hauchs Togter, 423, 20, 



Tab. I, Fig. 40—41. 

 1903. Esperclla lanugo Arnesen, Bergens Mns. Aarb. 1903, Nr. 1, 10, Taf. I, Fig. 6. 

 1903. Mycale lanugo Thiele, Arch, fiir Naturgesch. 1903, 381, Taf. XXI, Fig. n. 



Egg-shaped, or the larger specimens lengthened or quite irregular. The dermal membrane thin 

 pierced by the projecting spicula-bundles, and the surface therefore finely shaggy. In the regular, egg- 

 shaped specimens one single osculum, in the irregular ones several scattered oscula. The skeleton a rather 

 regular network of polyspicular, primary fibres and singly placed transverse spicules. Spicula: Megasclera 

 rather short, curved styli 0-166 — o-j/""": microsclera of one form , anisochelec palmatm 0-020 — 0-045""", 

 characteristic by their smaller end being comparatively large. 



This species grows almost always on Algce, on Hydroids, or on erect Bryozoa. The specimens 

 in hand are thus growing on Ptilota pectinata and on Odontlialia dentata; of Hydroids it is found on 

 Diphasia abietina, HydraUmania falcata, Gra miliaria abietina, Scrtularella sp., and Halecium ' sp., and of 

 Brvozoa on Micropora borealis. The smaller specimens are formed as regular round or egg-shaped, oftenest 

 flat cushions, and grow most frequently more or less unilaterally on the Alga or the Hydroid; when a 

 little larger they generally grow round it, but often keep a rather regular, somewhat flattened egg-shaped 

 form. In this condition, in which the sponge has a rather characteristic appearance, its longitudinal 

 extent is from 4 to 12 — i5 mm . When it grows larger it loses the regular form; thus it frequently in- 

 creases in length, and becomes longish incrustations 011 the branches of the Algae and Hydroids; it may 

 also grow more roundly and become large lumps spreading over several branches. This form, I sup- 

 pose, is most frequently formed by a coalescing of more individuals; such a coalescing, at all events, 

 is frequently seen and gives rise to irregular forms. The largest specimen in hand of this form is of 

 a greatest extent of 55' nm . The colour (in spirit) is lightly or more darkly yellow. The consistency is 

 swampv and slightly elastic. The surface is very finely shaggy from projecting bundles of spicules. 

 The dermal membrane is thin, has no skeleton of its own, but is supported by the projecting bundles 

 of spicules. The pores are found in the membrane, often close-set and in large numbers; most frequently 

 their form is oval, and they have been measured to sizes from 0-012 — o-i5' nm . Oscula. In specimens 

 of the regular, egg-shaped form only one osculum is found situated on one side; it is circular and of a 

 diameter of 1 — i*5 mm , its edge is most frequently slightly projecting. In the larger, irregular specimens 

 several oscula are found; sometimes each of them is placed on a slight projection, and this, perhaps, 

 is a mark of the original individuals that are coalesced into one specimen. 



The skeleton is of a quite regular structure consisting of polyspicular fibres. From the inmost part 

 of the sponge, that is to say from the part attached to the incrusted foreign body, which body, in the 

 sponges that are growing round it, runs through the middle of the sponge, fibres pass towards the surface. 



