85 PORIFERA. II. 



.somewhat shorter than in abyssicola. The size of the ancorte varies between 0'028 — o-034"" n , by far the 

 most frequent size is o-03i mm , the thickness in the middle of the shaft is ca. o-oo3 mm . Developmental 

 forms of the ancorse occur frequently in all stages, down to extremely fine ones, which are of about 

 the same length as the fully developed ones; in the very youngest stages both ends are as yet equal 1 ). 

 These voungest stages show in either end apparently only a hook-like recurving (PL XII, fig. 3 d) which 

 must, accordingly, be taken to correspond to the median tooth; but they are so fine and transparent, that the 

 real form of the end cannot be seen with certainty; in the stages a little older the teeth are seen. 2. The 

 large sigmata are of a regular sigma-shape, they are plane, or only slightly contort. Their outer 

 part, the recurving and the hook, is not quite cylindrical, but somewhat compressed. They vary in 

 length from cri2 — o-i6 mm , and in thickness from croo6 — o-oo9 mm . Developmental forms in different stages 

 of these sigmata were not rarely seen; the younger of these are more or less fine, evenly curved, and 

 long pointed staves without recurved ends; the ends are only developed by and by. Also the develop- 

 mental stages show the compression of the ends, and these are sharp inward. 3. The small sigmata 

 are of the same peculiar form as in abyssicola, with compressed ends, inwardly sharpened as edges. They 

 are likewise always contort to one fourth of a turning. Their length is 0-044— o-05i mm , and the thickness 

 in the middle is ca. o - ooi5 mm . The occurrence of this sigma is peculiar. It occurs always only very 

 sparsely, so that pieces of the sponge may be examined without any being found; but sometimes this 

 form of sigma seems to be quite wanting; thus in some specimens I have examined a great number 

 of pieces without being able to find it. Otherwise it is found sparsely in the tissue without any such 

 definite occurrence as in abyssicola. Neither does the large sigma occur in great numbers, but consi- 

 derably more copiously than the small one; it occurs in the layer of tissue and especially in the skin. 

 The aucorae are present in exceedingly great numbers, partly throughout the layer of tissue, but 

 especially in the skin or the outermost layer; they are especially closely packed in the thin layer of 

 tissue on the branchlets. 



Embryos. Round in the tissue embryos were found ; the}' lie singly in the layer of tissue 

 between the axis and the surface. They are all but globnlar and of an average size of ca. o - 3' mn . No 

 spicules were found in the specimens examined. 



This species, as will have been seen, is very closely allied to abyssicola, and it is mainly sepa- 

 rated from it by the constant difference in size of the three forms of microsclera. As mentioned under 

 the preceding species, I have seen a specimen from the material of The Norwegian North-Atlantic 

 Expedition of the species mentioned there by Armauer Hansen as C. abyssicola. It was a small 

 fragment, very much damaged, but it seems doubtless to belong to the present species. The size of 

 the ancorse is generally o-028 n,m , and that of the small sigmata o-o44 m,n . The specimen was from station 

 31 with a bottom temperature of -^-i°oC. Of the figures of the exterior in The Norwegian North- 

 Atlantic Expedition PI. YD, figs. 7 b, 10, and 12 would seem to belong to the present species. An 



M Carter, as is well known, advanced the theory that the anisochela; in their development pass through an iso- 

 chelate stage, because in a few species he had found large anisochehe and small isochelae together. He got this view on 

 account of his erroneous interpretation of the growth of the chete. The fact that forms as the anisancora; of the Cladorhi=a 

 begin with a stage where both ends are equal cannot, of course, corroborate Carter's 'theory, as his opinion was that an 

 isochelate stage fully developed as to form preceded the fiual, anisochelate one. 



