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Zoologie. — “On the spinispirae of Spirastrella bistellata (O. 8S.) 
Ldfd.” By Dr. G. C. J. Vosmarr, Professor at the University 
of Leiden. 
(Communicated in the meeting of January 30, 1909). 
Some years ago (1902) I drew attention to the fact that there is 
confusion with regard to the terminology of certain sponge-spicules, 
and tried to clear this up. I arrived then at the conclusion that the 
spicules, which are generally called “spirasters”, far from being 
a sort of ‘asters’, i.e. polyaxon spicula, ought really. to be 
considered as monaxons, the axis of which is a helix screw. I 
proposed for that kind of monaxons the term spirazon (Le. p. 105 
and 112). In order to avoid further confusion I called the spined 
forms: spinispirae. I had some doubts about the supposition of some 
authors, that transitions between true asters and spinispirae really 
existed, because I never found them and failed to find any proof in 
literature (le. p. 105). On the one hand authors make a certain 
distinction between true asters (euasters) and “spirasters”, but on the 
other hand consider both forms as belonging to the same group. 
Thus Torserr (1900 p. 21) distinguishes the genera Hymedesmia and 
Spirastrella on account of the fact, that the microscleres of the 
former genus are “euasters’, of the latter “spirasters”. It is generally — 
accepted that the microscleres of Hymedesmia stellata are euasters ; 
but with regard to H. bistellata there is diversity of opinion and 
confusion. I believe this to be due to an erroneous conception of 
the spicules under consideration. Although I was convinced for myself, 
that these spicules were by no means (polyaxon) asters, but (monaxon) 
spinispirae, I have tried nevertheless to produce proofs for my 
statement by carefully studying the spicules treated in various ways. 
More especially I was led to do this in order to settle the question 
between LENDENFELD and Topsent about the sponge, which Oscar 
Scumipt first described under the name of Tethya bistellata. Is it, as 
LENDENFELD suggests, a species of Spirastrella, or, as TOPSENT 
believes, one of Hymedesmia? Of course it is no Tethya; so far 
everybody agrees. 
Scumipt (1862 p. 45) described a sponge, which he called Tethya 
bistellata, a name which he altered himself into Suberites bistellatus 
(1864 p. 36). Now LenpenreLp believed to have traced the sponge 
in his collection from Lesina and called it Spirastrella bistellata 
(1897 p. 55). From this Torserr dissented in 1898, alleging that 
