PORIFERA. III. 



not seen, but as the papillae are nearly always somewhat contracted, it was also not to be expected, 

 that the pores should be visible. The two kinds of papillae are often recognisable already from their 

 outer shape, the oscular papillae being somewhat evenly couically pointed, while the pore-papillae are 

 more cylindrical in their outer part and have a stubby or cut end. Often, however, the papillae are 

 so strongly contracted, that it is not possible to distinguish them from each other so directly. In the 

 dermal membrane outside the papillae no pores were found. The structure mentioned of the papillae 

 has not been described hitherto, only Schmidt has some remarks about it, but he takes them all to 

 be oscula. For the rest he speaks about the peculiarity of the dermal membrane, remarking that it 

 consists of: "einer ausseren sarcodeartigen und einer inneren festen membranosen Schicht". From 

 his description of the papillae it is seen, that it is a pore-papilla he has examined, which are also 

 by far the most numerous; the fact is that he says: "Das Ende der Warzchen ist etwas verdickt, 

 der Gipfel scheinbar geschlossen, alleiu eine massige Vergrosserung zeigt, dass der Hauptcanal in 

 einer Anzahl Haarcanalchen sich nach aussen off net". The "Haarcaualchen" Schmidt has seen are 

 no doubt the inner cavity divided by the fibres, and his description is otherwise in the main correct, 

 only he takes the papilla to be an oscular-papilla. 



The skeleton. The dermal skeleton; the skeleton formed by the dermal spicules is not much 

 developed, it consists of larger or smaller bundles of dermal spicules lying in the membrane, partly 

 horizontally, partly more or less erect in the somewhat thick dermis; besides the bundles more 

 scattered and single spicules may also occur, but they are on the whole scarce, and large parts of the 

 membrane may be seen without dermal spicules. At the base of the papillae they are present in 

 greater numbers, and from here they stretch out in the wall of the papilla and form the skeleton of 

 the papilla as mentioned above. The main skeleton is a rather diffuse and irregular, multispicular 

 reticulation in which primary and secondary fibres cannot be discerned; also single spicules are in 

 many places seen to contribute to the skeleton. In the points of union is seen a distinct and rather 

 rich amount of spongiu which may also sometimes be seen to continue along the fibres. 



Splcula: a. Megasclera. i. The skeletal spicules are styli, they have an even, generally 

 slight curve, lying nearest to the rounded end. The apex may be somewhat different, partly in the 

 same individual, but especially in different individuals; it is generally of moderate length, but it mas- 

 be both shorter and longer, and it may be bounded by straight or curved lines; finally it may be 

 marked off in different ways; in a single specimen the point is often rounded and thus stubby. The 

 length of the styles may vary considerably, yet generally not much in the single individuals, but on 

 the other hand in different individuals; in all it is in the species between 030 and 0'68' nm , but only when 

 the sizes measured for all individuals are taken into consideration; as the common lengths may be 

 given C42 — o - 53 m,n . The diameter is on the whole o - oo7 mm — o-oi4' m ", but here also some difference is 

 present, in single specimens not reaching beyond con — O'oi2 mm . 2. The dermal spicules are tylota, 

 they are generally straight, sometimes slightly curved. They have a distinct, but often rather elongated 

 swelling at each end as a rule passing evenly into the shaft; this latter is sometimes somewhat poly- 

 tylote. Also with regard to this spicule the length varies somewhat from individual to individual and 

 follows herein the variation of the styles; the length lies in all between 0-25 and 04.7 m,n , generally it 

 is 0-32 — 0-41 ,nm . The diameter is about 0-003— o - oo6 mm , but sometimes does not reach the latter size. 



