fact whether the ideal axis lies in a plane or not. In the former 
case the line may of course be straight, curved, bent, flexuous ete. : 
in the latter case the line is a screw helix’). The spicula belonging 
to the former case I propose to call pedinarons*), the others 
spirazxons ®). To the group of the pedinaxons belong e. &. oxea, styles, 
however, to the spiraxons, that I wish more especially to draw 
attention. 
Again we can distinguish here two cases: a. the screw line is 
formed on the surface of a circular cylindre or 8. on that of an 
elliptical cylinder. The former group I wish to call a-spiraxons; the 
pitch is here generally large. The latter I call #-spirarons; the pitch 
is here small. 
Let us first examine the «-spiraxons. To this group belong the 
spicula known as sigmaspires, toxaspires, spirules; further those which 
are usually called spirasters and which are by the majority of spon- 
giologists erroneously considered as modified asters. This mistake is 
due, I believe, to Oscar Scumipt. „Eine blosse Modification dieser 
Kugelsterne,” he says, 1870, p. 5, sind die Spiralsterne oder Wal- 
zensterne. Sie werden zwar in manchen Spongien nur allein, d. h. 
nicht untermischt mit den Kugelsternen angetroffen (Spirastrella 
cunctatriv Sdt. Chondrilla phyllodes N.), haufiger aber, wie wir unten 
in die Specialbeschreibung (z. B. von Sphinctrella horrida N. und 
Stelletta hystrix N.) hervorheben werden, liegen alle Uebergange von 
den normal centralen Sternen zu den gezogenen Spiralsternen vor.” 
Unfortunately did Scumipr not keep his promise; for in the description 
of Sphinctrella horrida we find nothing more about it, and Stelletta 
hystrix is forgotten altogether. Scumipr failed, therefore, to give any 
proof whatever for his statement that /Spiralsterne” are modified 
“Kugelsterne’. ScHmipt’s suggestion has nevertheless generally been 
accepted, myself not excluded. 
SOLLAS (1888, p. LXI) distinguished two chief series of spicula 
(microsclera): “the radiate or astral, and the curvilinear or spiral.” 
The former are called “asters,” the latter “spires.” With some 
astonishment we further read that the asters are divided into two 
tylostyles, some of the “amphidisci’, some of the #toxa”. It is 
1) These terms are to be taken cum grano salis. No biological formation will 
ever be absolutely mathematical; thus it may be that the axis of a flexuous or 
undulating spiculum is not exactly lying in a plane, without, however, being in 
any way comparable to a screw helix. 
2) redivoc, plane, even. 
3) gmeita (lat. spira), everything which is twisted. 
