28 



PORIFERA. II. 



chelae vary very much in size. Their greatest length is 0-092""", but there may be a little difference 

 in different individuals, so that in some they reach at most o - o86 mm . The thickness of the shaft is ca. 

 0'005— o-ooy" 1 " 1 , and the greatest breadth is ca. 0030 — 0'035 mra . This largest form of the chelae may 

 vary a little in form in different individuals, especially the upper end may be a little shorter or longer. 

 From the greatest length the chelae may now vary down to so small a size as 0-025"""; at the same 

 time the dimensions of the several parts of the chela are also altered, the ends, especially the larger 

 one, becoming longer in proportion to the free middle part of the shaft. While thus in the large chelae 

 the larger end, the free middle part, and the smaller end are in a mutual proportion about as 2:2:1. 

 these parts are in the smallest chelae about as 2:1:1. In the series of variations of the chelae the 

 forms which would follow nearest to the largest ones, are of very rare occurrence, so that the chelae 

 would almost seem to fall in two groups, the larger ones only little varying in size, and the smaller 

 ones very varying in size. That such is the fact would also be implied by another thing, viz. that only 

 the large chelae occur in rosettes, while the small ones are never seen arranged in that manner. This 

 recalls to some degree the feature in several Dcswacd/a-species, in which only the larger of the two 

 occurring forms of sigmata are developed in bundles, while the smaller form is never arranged in 

 that way. Developmental forms of the chelae are also found, but most frequently only in very small 

 numbers; only in a few individuals they were a little more numerous. As the chelae they are found in 

 all lengths. The youngest developmental form I have seen, is an exceedingly fine staff recurved in both 

 ends, a little more in one end than in the other. During their growth as well the shaft as the recurved 

 parts grow thicker while in the curves the axis remain thin; the alae and the plate of the tooth is by and 

 by developed, by which fact the parts of the axis situated in them disappears or is effaced, while the 

 free middle part of the axis gets its final thickness. The part of the axis situated in the curve itself, 

 on the other hand, is not thickened, but keeps its original thickness, and from this part inward is 

 developed the thin plate, the socalled falx, connecting tooth and shaft. The falx is already developed 

 at an early stage. The chelae are found both throughout the sponge and in the dermal membrane, 

 as well singly as in rosettes; as above mentioned only the large ones are found in rosettes; these 

 rosettes are seen especially often in the pore membrane covering the furrows. The large chelae are 

 also found singly. 2. Sigmata; these are of the common form, and are almost always more or less 

 contort. Their length, which may be somewhat dependent 011 the degree of contortion, is between 

 0-017— 0-027"™; r ' ie thickness is between ca. 00008— oooi4 m, °. 3. Rhaphides; these are sometimes 

 seen singly, but most frequently in bundles, trichodragmata; the length of the individual rhaphides 

 varies from 0-043 — o , o85 ,nm ; such is the variation in the species, but in the single individuals it is not 

 so great, for instance 0-047— o-o67'" m an d 0064 — 0-085""". In individuals with the shortest styli also the 

 shortest rhaphides are found. The thickness is about o-ooi mm . The thickness of the bundles is 0-013 

 — o-oi8 ,nm . Sigmata and rhaphides occur both in the dermal membrane and throughout the sponge, 

 especially rhaphides in dragmata are of frequent occurrence in all parts of the tissue. 



Locality: Station 1, 62 30' Lat. N., 8° 21' Long. W., depth 132 fathoms; station 7, 63 13' Lat. N., 

 15 41' Long. W., depth 600 fathoms; station 55, 63 33' Lat. N., 15 02' Long. W., depth 316 fathoms. 

 Further it has been taken on 65 39' Lat N., 28 25' Long. W., depth 553 fathoms (the East-Greenland 

 Expedition 1891—92); 64 15' Lat. N., n° 15' Long. W., depth 192 fathoms (Wandel); the bay of Skage- 



