2o8 POR1FERA. II. 



ones had a longer point. 2. The dermal spicules are tylota with rather slightly swollen ends; they 

 are oftenest straight, more rarely a little curved. Their length is 0-34 — o-4o ,nm , and the thickness 

 ca. 0-0043— o , oo86 mra . The fully developed spicules have almost equal ends; the swelling of one end, 

 however, is most frequently a little more marked than that of the other; the finer the spicide is, the 

 more distinct is this feature, and the very finest ones are quite monactinal. b. Microsclcra ; these are 

 of three forms, isochelas arcuatse, forcipes, and sigmata. 1. Chelae arcuatae are of a similar structure- 

 as in the preceding species, F. Topsaitii, but they are smaller; they have an evenly curved shaft, a 

 more or less broad oval tooth with a triangular tuberculum, and the alae are of the same length as the 

 tooth. Their length is 0-021 — o-033 mm , and the thickness of the shaft is ca. 0-0021 — ooo28 mm . 2. For- 

 cipes; these are of only one form, and they are rather characteristic; they have a round curve above, 

 and one leg is considerably longer than the other; the legs are slightly diverging in their upper part, 

 then the shorter leg bends a little more outward, and the longer leg does the same, but this latter 

 bends again inward, so that it forms an even, slight curve with the convexity turned outward. This 

 is the typical form (PI. XIX, Fig. 5 d), but various deviations may be found. Thus they may be some- 

 what twisted, and the legs may be of equal, or about equal, length, and in this case they are often 

 more or less uniform, both forming a curve. By slight enlargement the forcipes appear to be slightly 

 spined, but under higher magnifying powers the}- are seen to be rather finely, but densely spined; 

 the legs end in a button-shaped swelling. Their length, measured from the curve to the end of the 

 longer leg, is 0-037— o■o6o ,, " I, , and the thickness at the curve is ca. 0-0014— ooo28 mm . A few, quite fine 

 and smooth developmental forms were seen. 3. Sigmata are of the common sigmaform and are 

 plane or almost plane; they vary in length from o-n — 0-13""", and in thickness from 0-0057 — o - oo7 mm . 

 A few fine developmental forms were found , not yet provided with recurved hooks. The micro- 

 scleres occur throughout the sponge and in the dermal membrane; in the pore sieves chelae seem 

 especially to be found. 



Note. In the dermal membrane and in the membranes of the canals granulous cells, cellules 

 spheruleuses , are found abundantly. They are roundish or longish, of an average size of o-oi5' nm , and 

 filled with rather large, refracting granules, in spirit their colour is white. Frequently the walls of 

 the cells have disappeared, so that the membrane is seen to be filled with granules, more or less gath- 

 ered in groups. 



Embryos. In some of the specimens embryos were found in great numbers in the tissue. They 

 are globular, of a white colour, and their average diameter is o - 23 mm . Some of the examined specimens 

 showed no spicules, others had spicules, and then both megascleres and microscleres were found. The 

 megascleres are somewhat interesting; they are slightly- curved, somewhat club-shaped styli, sometimes 

 with a slightly marked head; they attain a length of up to o-i2 mm The most interesting feature is, 

 however, that the}- are slightly rugged -spined; as Forcf/>ia-species with spined spicules exist, 

 one is led to suppose that the spinulation ma}- possibly be a primary character, and that species with 

 spined spicules ma}- be more primitive than those with smooth spicules. A fact leading to the same 

 conclusion has been mentioned under some of the species treated above; thus AI. fiedunculata has 

 smooth styli, but its embryos have spined styli, and M. pluridentata has smooth styli, but the fine 

 developmental forms are slightly rugged. - - The microscleres are only chelae, the}- are of the same 



