1165 
not abundant; in some cases they are exceedingly scarce and 
only discovered after looking through many sections. What we have 
said about the chelae likewise holds for sigmata. If microsclera are 
present, generally a few acanthostyli occur; but it sometimes happens 
also that the latter “are present, without any microscleres being 
found (1090). Taking everything together we get the impression 
that the sponges under consideration are deseendants from forms 
with a full set of spicules: styii, acanthostyli, sigmata and 
isochelae. 
If the scarlet crusts mentioned above oceasionaliy possess such a 
small quantity of acanthostyli or microsclera that these are only 
discovered after long searching, there is a fair chance that we shall 
meet with. specimens in which the additional spicules are entirely 
absent and in which the skeleton is composed of styl only. At 
any rate the absence of accessory spicules does not prevent us from 
identifying our specimens with already described sponges of which it 
is stated that they possess only styli; of course if they agree in other 
respects. I do no thesitate, therefore, to recognise a close relation 
between our crusts and two sponges formerly described, viz. Spongia 
sanguinea Grant and Hymeniacidon caruncula Bwk. The former was 
subsequently likewise brought to the genus Hymeniacidon and Torsent 
even advocated the identity of both. He writes (1900 p. 261):.... “je 
crois bien que FÉponge désignée par BowrrBank sous le nom de 
Hymeniacidon sanguinea west pas différente de celle qu'il a appelée 
Hymeniacidon caruncula’. Miss Stupnens (1912 p. 37—38) I under- 
stand, arrived at the same result and I can but agree with these 
distinguished spongiologists. 
Now there is among the Sponges from the Bay of Naples a 
remarkable specimen (16), which covers the rhizoma of Posidonia. 
In some places it is a mere thin crust, in others it is thicker and 
exhibits knobs and lobes and ridges. In such places it looks rather 
massive, but sections show that in reality the whole sponge is hardly 
more than a crust. Besides this specimen there are several others 
in my collection which possess such lobes and ridges, which are 
prolongations from the general encrusting base. In this connection 
Jonnston’s observation on “Halichondria sanguinea” (= Spongia 
sanguinea Grant) is worth noticing. He says that the sponge occurs 
in crusts; but he adds (1842 p. 134): “MH. sanguinea occasionally 
occurs in amorphous masses of considerable size and thickness with 
very uneven or ragged surface”. Further I draw attention to KOLLIKER’s 
statement that some of the spicules of a sponge which he determined 
as Halichondria sanguinea possess short spines (1864 p. 56). 
