PORIFERA. II. 203 



on the other hand, is larger and more distinctly marked. The younger the tylotes are, the more 

 marked this difference is. The shaft of the tylotes often shows slight, irregular thickenings, so that 

 they may approach polytylota. b. Microsclera; these are of four forms, isochelse arcuatse, forcipes of 

 two sizes, and sigmata. 1. The arcuate chelae have an even and not much curved shaft; the tooth 

 is narrowly elliptical, and there is a longish, pointed tuberculum; the alse are tooth-like and of about 

 the same length as the tooth. The chela may be of a somewhat varying form, the tooth and alae 

 especially may be shorter or longer in proportion to the total length. The length is 0-042— 0-057™™, 

 the thickness of the shaft is 0-0042 — ooo57 mm . A few developmental forms were seen. 2. The large 

 forcipes are of a form quite like that figured by Vosmaer I.e. They have a round curve above and 

 two parallel, or quite slightly converging or diverging legs; only rarely the legs are more diverging. 

 The legs are of equal length, or there may be a quite slight difference in this respect; the)- end in a 

 little swelling. The forcipes are spined; under small magnifying powers the spinulation looks some- 

 what rugged, but by sufficient enlargement (ca. x 1000) it is seen to consist of well developed spines 

 directed backward and somewhat compressed; they are, moreover, rather distinctly arranged in rows. 

 By this enlargement the swelling at the end of the legs is seen to be a semiglobular knob attached to 

 the leg by the flat side; this knob is somewhat spined or indented in the edge. The forcipes are 

 frequently a little twisted. Their length is 0-060— o-oyy mm , and the thickness in the middle of the legs 

 is ca. o-oo29 mn '. Of forcipes a few developmental forms were found, the finest ones are quite smooth, 

 and the ends of the legs are finely tapering without any swelling. 3. The small forcipes have a 

 quite similar form as the large ones, only they are much smaller, and the difference between the 

 lengths of the legs is most frequently a little more marked; they are also spined, quite in the same 

 way as the large forcipes. Their length is 0-025— o-034 mm , aim tne thickness in the middle of the legs 

 is about o-ooi mtI1 . 4. Sigmata; these are rather large, they are of the common sigma-form, and are 

 plane or a little contort. Their length is rather constant, 0-12— o-i4 mm , and the thickness is 0-005 — 

 o-oo7' nm . Of the sigma a rather great number of developmental forms were seen, the youngest stages 

 were very fine and had as yet no recurved ends. The microscleres are found through the whole sponge, 

 as well in the skin as in the other parts of the body; in the membrane coating the bottom of the 

 pore grooves, the chelae are found very abundantly, but none of the other forms. 



Note. In the skin cellules spheruleuses are found in great abundance; they appear as more 

 or less distinctly limited crowdings of refracting granules; often the boundaries of the cells are effaced, 

 so that the dermal membrane appears closely filled with refracting granules more or less gathered 

 in groups. 



Embryos. Round in the tissue some embryos were found scattered. They are globular, of an 

 average size of o-35 mm . Most of the examined specimens showed no spicules, some exceptions were, 

 however, found. These latter had microsclera, but only chelae, which is thus the first occurring form; 

 they occurred abundantly at all stages of development, from fine staves to almost quite developed 

 spicules. They are smaller than the chelae of the developed sponge, being from 0-030— o-035 mm long. 



Remarks: From Schmidt's description cited above, this species would not be recognisable at 

 all, and the two figured chelae do not even belong to it. Thiele, however, has examined the type specimen, 

 and from his description and figures I have been able to identify the species with certainty, although 



26* 



