PORIFERA. II. 



the common way spread in a fan-shaped manner in the longitudinal direction, so that in a transverse 

 section it appears to have only the thickness of a couple of spicides. Accordingly the fibres pass from 

 the middle of the axis through the layer of tissue surrounding the axis, and through the branchlet 

 to its point. In the layer of tissue coating the stalk and the branches, as far as I have been able 

 to see, only rather few, scattered spicules are found. In the stalk and the branches the spicules 

 are cemented by a clear mass of spongin; it coats, no doubt, the whole fibre with a thin layer of 

 spongin, but forms no visible sheath. In the lower part of the stalk it may become somewhat 

 more copious, and then the otherwise white, transparent axis becomes here a little yellowish. In the 

 branchlets no spongin was observed. 



Spicula: a. Megasclera are styli; they are straight or quite slightly curved; they are fusiform, 

 tapering more or less towards the head-end; not rarely their outer part has a special, but slight taper- 

 ing. The opposite end tapers evenly; the point proper may be somewhat varying, but is always 

 short or rather short, not rarely quite blunt or rounded. The spicules of the axis and the branchlets 

 are of the same form and cannot be said to fall under two distinct groups, but upon the whole there 

 is, however, some difference as to size between them, so that the axial spicules are averagely larger 

 than those of the branchlets. The length of the axial spicules is about 0-5 — 073™™, and the thickness 

 from 0-013 — o-oi9 mm . The spicules of the branchlets are generally 0-39 — o-47 m,n long and 0-007 — ca - 

 o - oi3 mm thick. All kinds of transitional forms occur however. Thus upon the whole a variation is 

 found in the spicules as to length from 039 — o73 mm and as to thickness from 0-007 — o^oig™"". Besides 

 by their size the styli of the branchlets deviate also from those of the axis by having a longer 

 point, and moreover they show also a little curve at the head-end, about as figured and described bv 

 Sars. Sars says that such spicules only occur at the point of the branches; the fact is, however, that 

 they form the fibres of the branchlets, and accordingly they are also found in the points of the 

 branches, where the branchlets are close together; the mentioned curve may otherwise also be found 

 in axial styli. b. Microsclera; three forms occur, anisaneorse unguiferse and sigmata of two forms 

 and sizes. 1. The an corse are of the structure typical of Cladorhiza with a regularly curved shaft 

 and five distinct, narrow, lanceolate teeth in either end; a considerable difference is found between 

 the sizes of the two ends. The larger end has on either side of the shaft a narrow ala somewhat 

 longer than the teeth. A sure view of the number and form of the teeth is only to be obtained 

 by regarding the ancorae from the end. Sars, in the work quoted, says that the ancorse have three 

 teeth, but that some have five, and continues: Whether this applies to all or only to some the 

 position of which happened to be more favorable, I am not able with certainty to decider '). The 

 real fact is that the ancorae have always five teeth in either end. The size of the ancorae is only 

 little varying, their length from ox)2i — o-025 m,r -, and the thickness of the shaft is ca. o - oo2 mm . A few 

 developmental forms of the ancorse were also seen, in the finest ones the ends are as yet only little 

 developed, and they are equal or about so, but a difference in size appears very soon. 2. The large 

 sigmata have a regular sigma-form ; they are always plane or about plane. Their length is between 



') It is evident that the opinion of Sars is that the ancorae, what he has not been able to decide with certainty, 

 may possibly always have five teeth, but that this fact is only to be seen, when the ancora? are favourably situated, but his 

 expression, to be sure, says really something different. 



The Ingolf-Expedition. VI. 2. 1 1 







