PORIFERA. II. j6i 



this, be taken to be more or less leaf-shaped, presumably with a broad base. The largest fragment 

 has a height of 45 mra and a thickness in the leaf-shaped part of 8 mm . The colour (in spirit) is light 

 yellowish. The consistency is rather firm, but brittle. The surface is almost smooth or only very 

 slightly shaggy, and the shagginess is chiefly due to the large chelae, lying closely in the membrane. 

 The dermal membrane is a thin film, supported by bundles of dermal spicules. The pores are closely 

 gathered in sieve-like areas, often so close as to be separated only by thin strings; their size was 

 measured to 0-09 — o7o mm . Oscula are circular openings of a diameter of ca. 2 mm . To judge from the 

 material, the pores are situated on one side, and oscula on the other. 



The skeleton. The dermal skeleton consists of bundles or short fibres of dermal spicules spread 

 in a penicillate way ; they issue from the skeleton below and reach mostly horizontally into the mem- 

 brane. When a piece of skin is cut off and seen from above, the fibres are seen especially to issue 

 from the edge of the subdermal cavities or the incurrent canals, over which the pore areas are ound 

 then they pass into the area and send off branches into the strings between the pores. Also on the 

 oscular side the construction of the dermal skeleton is similar, the skin over the numerous canals that 

 pass the sponge about transversely being also supported by short fibres. The membrane is, moreover, 

 filled with chelse, especially of the largest form. The main skeleton is chiefly constructed as in fragilis, 

 and forms an irregular network of triangular, quadrangular, or polygonal irregular meshes. It is 

 generally polyspicular with rather many (4 — 8) spicules alongside. No distinction can be made between 

 primary and secondary fibres; here and there a little longer fibres may be found running in the longi- 

 tudinal direction, but continuous fibres are otherwise not formed. When a section placed in xylole is 

 examined, all the canals are distinctly seen, as the membranes coating these canals are highly filled 

 with chelae. Spongin is found in the skeleton, but it is white and clear, and only a very small amount 

 is present. 



Spicula: a. Megasclera. 1. The skeletal spicules are acanthostyli with rather dense spinu- 

 lation. They are evenly and slightly curved, and have a middle long point, which is, for a greater or 

 smaller part, without spines. Their length varies from 0-34 — 0-429™"", the shortest ones being rather 

 rare; the thickness is ca. 0-0128 — o-02i mm . A few developmental forms were found, the finest ones, of 

 a thickness of ca. o-oo2 mm , were seen to be finely spined. 2. The dermal spicules are tornota; they 

 are straight or, more rarely, a little irregularly curved. They resemble the tornota in L. fragilis, and one 

 end is a little thicker than the other, which is somewhat longer pointed ; in the finer forms this feature 

 is most marked. Their length is 0-238— o-28 mm , and the thickness 0-0047 — o-oo6o mm . b. Microsclera. These 

 are chelse arcuatse of three forms and sizes, and sigmata. 1. The large chelse are very characteristic; 

 their shaft is strongly curved, almost to a semicircle, and the terminal parts are relatively small; 

 the tooth is short and stubby, and the likewise stubby alse are of the same length as the tooth. Their 

 size is somewhat varying, the length from 0-047 — o-07i mm , most frequently it is nearest the latter size; 

 the thickness of the shaft is 0-0057 — o-oi4 mm ; this variation in thickness is due to the fact that the 

 shaft is not cylindrical, but somewhat flattened, and therefore a transverse section of it is elliptical. 

 Of this chela some developmental forms were found; the younger these forms are, the more flattened 

 is the shaft, so that it may be quite thin, almost band-shaped. A transverse section shows, however, 

 that a thicker part is running through the middle of it, while the lateral parts are quite thin; then 



The Ingolf-Expedition. VI. 2. 21 



