146 



POR1FERA. II. 



end corresponding to the point; they are otherwise of the same form as the styli, but are spined 

 throughout their length, and the spines are generally more close-set, not only at the basal end, but 

 also at the apical one. Although styli and strongyla are certainly nothing but modifications of the 

 same form of spicule, which is also seen by the fact that the strongyla seem upon the whole to be a 

 little shorter than the styli, no transitional forms, or, at all events, only very few ones, are found 

 between them. The length, which may be given collectively for styli and strongyla, varies from 0-238 

 — 0-38"™, and the thickness from ca. 0-012— o-02i ram , the longest ones being far from always the thickest 

 ones. Developmental forms were found, but only in very slight numbers; these forms were always 

 long pointed, and consequently I suppose the strongyla to begin as styli. The developmental forms are 

 finely, a little ruggedly spined, and they show not rarely a head-swelling. 2. The dermal spicules 

 are tornota; they are straight, cylindrical, often quite slightly fusiform. Their ends are slightly swollen, 

 about pear-shaped, with the end turned outwards; they have a similar structure as in rosacea, being 

 cut off and having, as far as could be discerned, two to four small points. This form of the ends is, 

 however, much less conspicuous here than in rosacea, and it is only to be seen distinctly under high 

 magnifying powers. The two ends of the tornotes are not equal, one being a little thicker than the 

 other. Their length is 0-20— o-2o, m,n , and the thickness is 0-004 — o-ooy"" 11 . Developmental forms wen 

 seen in small numbers, the finest ones are styli with one end pointed; by and by thev get their final 

 form. b. Microsclera are isancorse spatuliferse of two forms, larger and smaller ones. 1. The large 

 aucorae are mainly similar to the ancorae in fimbriata ; they have an evenly curved shaft and distinct, 

 rather broad alae a little longer than the teeth. The alae approach each other closely and are very 

 often connected by a narrow rim along the middle of the shaft as in rosacea. The ancorae may be 

 somewhat varying in form especially with regard to the length of the terminal parts in proportion to 

 the total length, and accordingly with regard to the length of the teeth, the ends of which may thus 

 approach each other more or less. Their length is 0-053— 0064""", a "d the thickness of the shaft 0-005 — 

 o-oo7 mm . 2. The small ancorae are more slender, the shaft may be a little more or less curved, the 

 terminal parts are comparatively longer, so that the teeth approach rather closely in the middle; the 

 teeth are leaf-shaped and most narrow at the place of attachment. Also in this ancora the alas approach 

 closely or are connected in the middle by a rim. Their length is 0-027— o-034 mm , anc ^ the thickness of the 

 shaft is about 0-0014 — o - oo2 mm . Developmental forms of both ancorae occur at all stages. The ancorae 

 are found throughout the sponge and especially in the dermal membrane, often very abundantly; the 

 small ancorae are far more numerous than the large ones. -- Some difference as to the size of the 

 spicules may be found in different individuals; a specimen from the Davis Strait had spicules still a 

 little larger than the given measures, its skeletal spicules reaching o-44 m,n , the dermal spicules 0'35 miT1 , 

 and the large ancorae 0-069""", while, on the other hand, the small ancorae did not exceed the given 

 measures. 



Embryos. In some individuals embryos were found; they are scattered in the tissue, are 

 globular, and of an average diameter of o - 3 ,nm . Of spicules the examined specimens had both mega- 

 scleres and microscleres. The megascleres are straight, rather coarsely spined subtylostyli of an 

 average length of an 1 "" 1 and a thickness of o-oo^j mm . Of microscleres only the small ancora was found, 

 it was of normal size. The megascleres were lying in a bundle, all with the head-eud turned the 



