58 PORIFERA. I. 



the low prominences mentioned above. x\s to the other skeletal structure, I have not been able to 

 decide with certainty, whether concentric lamellae are foimd here as in G. litridus\ but it would seem 

 so, as a layer, constructed in the same way as the dermal layer, is found a little way within this latter. 

 The other inner skeleton, as far as I have been able to decide, consists of an irregularly polyspicular 

 reticulation. As in G. luridus, the spicules of the dermal layer and of the lamellte inside are, at the 

 points of intersection, and not only at the ends, united by spongin; but in the present species the 

 spongin is only found to a very slight degree; the amount of spongin is also ver\- slight in the other 

 parts of the skeleton. 



Spiciila: a. Megasclera are oxea, slightly, sometimes a little irregularly curved, and rather 

 shortly pointed; the length is very constant, and is between 0-62 — 0-68""", the thickness is 0-014 — o-oi/™'", 

 finer, to very fine oxea are found, but only in very small numbers, b. Microsclcra : i. Toxa; these 

 are exceedingly small and fine; their form is obtuse-angled to rectangular, and they have, at all events 

 the larger ones, a little recurved point; upon the whole the}- resemble the small toxa in the preceding 

 species, being only more frequently rectangular or about so. Their length is O'Oi — 0-02""", the thickness 

 is less than o'coi""". 2. Sigmata; while in the present species the toxa are smaller than in luridiis^ the 

 sigmata are larger; they have the common form, but sometimes they have a sharp curve in the middle, 

 and so the\- resemble the sigmata of hiridits\ upon the whole they are often somewhat irregular and 

 angular in the curve. The length is somewhat varying, from 0-035 — 0-078""", and the thickness is in 

 proportion 0-0018—0-003""". In this species I have found developmental forms of sigmata; as was to 

 be expected beforehand, the sigma is begun in about its full length, and it grows only in thickness 

 and so far in length, as the recurved ends are formed and get their full length. The developmental 

 forms I have found, which are only very few, are characterized as such b>- being fine, and not, or 

 only to a small degree, having the ends bent in a hook-like manner; the length may be varying, and 

 has, for instance, been measured to 0-05""". It is accordingly seen that the growth only takes place 

 by apposition, and so it is proved that the small sigmata that are fully developed as to form, are not 

 developmental forms of the larger ones, but are sizes that are present together with the larger ones. 

 As well sigmata as toxa are present in large niimbers throughout the sponge; besides sigmata are 

 seen in rather large numbers in the skin, while toxa are not found there. 



Roiiarks: As in G. Inridus < cellules spheruleuses Topsent are found in large numbers in the 

 present species, but here they are only found in the dermal layer — and in the layer inside the skin 

 mentioned in the description — ; their occurrence in the dermal layer is rather peculiar; that is to say 

 they are partly found scattered, but partly also closely gathered into bandshaped groups with a di- 

 rection longitudinalh' of the sponge. These bands are distinctly visible to the naked eye or through 

 a lens, and they convey an impression of being spiculo-fibres ; it is only under the microscope that they 

 are seen to be formed by the close-gathered cells (PI. XIII, fig. 10). The average breadth of the bands 

 is about o-ii — 0-15""". The cells are roundish, elongated, or fusiform, sometimes produced at. both ends 

 to fine processes. Their colour (in spirit) is light yellow; averagely the\- are larger and with larger, 

 more refringent granules than those of liiridiis. The roundish ones have an average size of 0-008— o-oiy'"", 

 the elongated ones reach a length of ca. 0-035""". Those scattered in the skin, are the greatest, and 



