9 6 



PORIFERA. II. 



formation and arrangement of the skeletal axes may in certain places be .somewhat modified by 

 coalescings between the axes and the small fibres of the stem and the branches in near the axis of 

 the stem, so that in these places a quite irregular network of fibres is formed (PL III, fig. 8). These 

 coalescings, which are evidently secondary ones, seem to me to corroborate the view advanced above by 

 showing that coalescings easily take place. Outside the axes and the small fibres a great number of 

 scattered spicules is found in the tissue; they may here and there gather into bundles or short fibres, 

 and the}' support also the dermal membrane as a rather dense, but irregular network of scattered 

 needles. In the axes a tolerably copious, slightly yellowish mass of spongin is found imparting to the 

 axes a yellowish, hyaline appearance. 



Spicula: a. Megasclera are styli, almost always quite straight; they taper somewhat towards 

 either end, and are therefore markedly fusiform ; the rounded end may be more or less thin, sometimes 

 it shows outmost a more abrupt tapering. The point may vary somewhat in length, but is always 

 short or rather short, a more abrupt, distinct point being found besides the even decreasing in thick- 

 ness from the middle; sometimes the outermost point is especially marked off. There is no difference 

 between the styli of the axis and those of the other parts of the body. The length is rather constant 

 and varies from ca. 0-56- 071""", and the thickness from ca. 0015 — 0'024 mm . Finer developmental forms 

 are onlv seen quite singly, b. Microsclera are of three forms, anisancorae unguiferse and sigmata of two 

 forms, larger and smaller ones. 1. The ancorse are of the common C la dor h/za -lor m and have five 

 teeth at either end; at the larger end rather broad alse are found somewhat longer than the teeth. 

 Sometimes six teeth are found at the larger end. The length varies from 0-033— o-037 min , and the thick- 

 ness of the shaft is about croo28 min . Developmental forms in different stages are also found. 2. The 

 large sigmata are of a quite peculiar form, the shaft is only slightly curved, the recurved ends 

 are prolonged in a flagelliform way to a fine point. The surface of the sigma is a little uneven, so 

 that the contour appears somewhat undulated, especially in the middle. The ends are not cylindric, 

 but a little compressed. The sigma is contort to a somewhat different degree, most frequently up to 

 about one fourth of a turning. The length is between 015 and o-i8 mm , and the thickness in the middle 

 of the shaft is ca. ooo7 mm . Of this sigma a few developmental forms were seen, the youngest ones 

 only representing the shaft without curves, those a little older having short curves; in the latter the 

 compressed form of the ends is distinctly seen. 3. The small sigma occurs only in the ends of the 

 branches, and has from this fact, I think, been overlooked by Carter. It is of a quite similar form as 

 the sigma occurring in the same way in the preceding species, for instance tenuisigma, and evidently 

 corresponds to this sigma. The shaft is about straight, the ends are recurved and a trifle compressed 

 about from the middle of the sigma. The sigma is contort, most frequently one fourth of a turning. 

 The length is 0-057— 0'074 mm , and the thickness in the middle is ca. o-oo2 mm . The aucoras and the large 

 sigma occur everywhere in the sponge, especially in the dermal membrane everywhere in the cavities; 

 the small sigma, as mentioned, occurs only in the points of the branches and in rather small numbers. 



Embryos. Embryos are found in great numbers everywhere in the sponge. The)- are more 

 or less oval and a little flattened. Their longest diameter is on an average ca. 0'42 mm . They were 

 found partly without spicules, partly with microscleres. These were ancorse, and as in the preceding 

 species we have again here the peculiar fact that these ancorae are of a different type from those of 



