io 6 PORIFERA. II. 



alee continuing down along the shaft and being a little longer than the teeth. The length of this 

 aneora varies from 0-057 — o-oyj mm , and the thickness of the shaft is about o-oo4 mm . Younger forms in 

 different degrees of development are also found. 2. The small ancorse have a rather highly curved 

 shaft, but there may be some difference in the degree of curving; the number of teeth may be different, 

 from six to nine, it seems most frequently to be seven or eight. Some irregularity is not rarely seen, 

 so that some teeth are larger than others, or that more teeth are found on one side of the median line 

 than on the other. Some instances are also found, in which the number of teeth at each end is 

 different, for instance six and seven. At either end of the shaft two small alae are found. The direc- 

 tion of the teeth is somewhat varying in this aneora, so that they are either directed almost horizon- 

 tally outward, or more or less downward, i. e. towards the middle. The length is rather varying and 

 is between 0-018 and 0-03"™, and the thickness of the shaft is ca. o-oo28 mm . Developmental forms of 

 this aneora were seen quite singly. 3. S i g m a t a ; these are of a form quite similar to those occur- 

 ring in most Clador/i iza-species, with compressed, inwardly edged terminal parts; they are also contort, 

 almost always one fourth of a turning. Their length varies from 0-037 — o-045 mm , and the thickness in the 

 middle is ca. o-oo2 mm . The ancorse occur everywhere in the sponge in tissue and in dermal layer; they 

 occur also in the axis in the tissue between the single fibres of which it consists; at the point of the 

 papillae the small aneora is wanting, or is only present in small numbers. Sigmata occur only in the 

 papillae, especially at the point, and they are not of equally frequent occurrence, being more scarce at 

 the point of some papillae, while in others they are found more copiously. 



Embryos. Embryos were found in one of the two smaller specimens; they were rather con- 

 spicuous, as they are very large, and shine through the surface on account of their deeper yellow 

 colour. They are uncommonly large, reaching a diameter of 5 mm ; they are round, most frequently much 

 flattened so as to become almost discoid or lenticular. They are placed in the body of the sponge 

 between the skin and the axis, often in such a way as to be lying partly in the soft tissue, 

 partly in the hard outer layer, sometimes also entirely in the outer layer in lenticular cavities; in the 

 latter case the surface may be bulged out by them, and the layer separating them from the surface 

 may be rather thin. Of spicules they have both megascleres and microscleres. -The megascleres are 

 thin and fine styli, quite reminding of developmental forms of the styli of the grown sponge; their 

 greatest measured length was o-8o. mm . Of microscleres the large aneora occurred rather abundantly, 

 and a few developmental forms of this aneora. These ancorse are somewhat deviating from those of 

 the grown sponge, their shaft being thinner and their teeth somewhat longer. Also the small aneora 

 occurs, but only in very small numbers. Then forms occur, also in very slight number, that are, as 

 to size, transitions between the two kind of ancorae, so that we must suppose the possibility that the 

 cells forming the ancorse are not from the beginning distinctly separated into two kinds; it is, to be 

 sure, to be supposed that later, when the ancorae are found as two distinctly separated forms, each of 

 these is formed by a distinct kind of cell. The large ancorse in the embryos are of full length, they 

 were even measured to be a little longer than has been observed in the grown sponge, viz. to o-o84 mm . 



As I have had type specimens of all the four species established by Armauer Hansen, I 

 have been able to decide with certainty that they belong all to one species. Three of the species, 

 clavata, nucleus, and arctica . are only loose papillae of gigantea , and it is a singular thing that 



