PORIFERA. II. 31 



cannot be drawn; these spicules do not vary much in length in the different individuals, and the 

 smallest length of the needles, therefore, is rather constant. The greatest length of the needles, on 

 the other hand, varies much in different individuals, and this length is dependent on the length of 

 the point, so that the longer and finer the point is, the longer is the needle. The boundaries of the 

 length of the styli upon the whole in the species are 0-53 — ri5 mm , but when given for separate indivi- 

 duals, the length of the point being also taken into consideration, we get for instance 0-56— o-So^"" 1 

 the point more or less rounded; cr6o— o'95 mm the point short; 0-65— i' m " the point rather long; 0-65 — 

 ri5™ the point very long. The thickness of the needles is somewhat varying, and the longest ones 

 are far from being the thickest ones, the mentioned transverse spicules being both the shortest and 

 the thickest; the thickness is between ca. o-oi3 mm and cro2 mm . Some difference may be found in diffe- 

 rent individuals, especially with regard to the greatest thickness, which sometimes does not exceed 

 o-oi8" ,m . Finer developmental forms are seen, but only singly, b. Microsclcra: these are anisochelse 

 palmatse, sigmata, and rhaphides in trichodragmata. 1. The anisochelse are of the common Mycale- 

 type and constructed in almost quite the same way as the chela; of the preceding species, the only 

 difference being that the tooth of the upper end is broader. The greatest length of the chelae is 

 o-oo,2 mm , but there may be some difference in different individuals. The thickness of the shaft is ca. 

 o-oo8 mm , and the greatest breadth is 0-028— cro4 n,m . From the greatest length the chelae vary in size 

 down to o-028 mra , and at the same time the proportionate dimensions of the different parts are altered 

 in a similar way as in the preceding species. The chelae are not rarely a little twisted. Also in the 

 present species a break is found between the large chelae and the largest of the smaller ones, and also 

 here only the large chelae are found in rosettes. A few developmental forms were found quite corre- 

 sponding to those in placoidcs. 2. Sigmata of the common form, often somewhat irregular and more 

 or less contort; their length, which is much dependent on the curve, is between 0-021 and o-032 mm , 

 and the thickness varies from o-ooio— oooi5 mm . 3. Trichodragmata; the single rhaphides are of 

 a length of 0-042— o-078 mm , most frequently about midway between the two sizes; the thickness is 

 00008— o-ooi4 mm . The rhaphides are almost only seen in trichodragmata, of a thickness of o-on— 

 . 0I ^mm Th e microselera are numerous throughout the sponge, sigmata are of especially frequent 

 occurrence in the dermal membrane. The large chelae occur in many places, in rosettes in enormous 

 numbers. 



Remarks: In the above mentioned largest specimen taken at Upernivik, there are found here 

 and there in the sponge, but in very small numbers, some peculiar spicules that may be designated 

 as tylostrongyla, and whose form may be seen in the annexed figure (fig. 1), which represents three 

 of these spicules and the end of a fourth, and shows different forms of the end-swelling. One end is 

 rounded, while the other is swollen to a more or less pyriform expansion. These spicules always 

 occur in a particular way being only found in the projecting bundles of spicules, always only one or 

 a few spicules in the same bundle, and only here and there, so that many of the projecting bundles 

 may be examined without any being found. In the bundle they are always placed with the swollen 

 end outward, so that it is seen between the points of the other projecting spicules. It is easily seen 

 that these spicules, with the exception of the swelling, are in all other respects of quite the same 



