2 
they did not possess such characters as seemed to me to have a 
specific value. They are varying in size, colour, shape and spi- 
culation. But as never a correlation of this distinetive was to be 
observed, so I thought it without doubt the most practicable way 
in uniting them to one single species. Haeckel, Schmidt andF.E. - 
Schulze have deseribed several species that show plenty of varieties. 
Most of the Calcareous Sponges, our common Sponge (Kuspongia 
officinalis), Spongelia pallescens a. o. are instances. 
Observations on Thenea muricata Gray again have proved to 
me that in several Sponges there are to be discerned two kinds of 
spieules; viz. such as are characteristic for the species, and others 
which often occur so few in number that their presence or absence 
never can be a distinetion. I propose to call „specific spicules” 
those which are a „conditio sine qua non’ for the species: which 
are characteristic for it. Those spicules which form the character 
of the genus may be called „generic spicules’” as f. i. the well- 
known palmato-inequiended anchors for Esperia. Now it is to be 
noticed that these spicules can occur in other species or genera; but 
in that case the whole combination of spicules form the character. 
For this combination of spicules I propose the general term of 
„indicating spicules” („spicula indicantia”). I need not say that 
when this term is used in the diagnosis of a species, the specific 
spicules are meaned, in other cases „subspecific’”’ (subspecies = va- 
rietas), generic spicules etc. 
As for the formulas or signs, used in the following lines, I must 
refer to my paper on this subject !). In the spieules of Tetracti- 
nellidae the angle ® can be >, <or=90°. I must however say 
that ee not is to be taken in a striet mathematical sense; 
®=90° is written when the three teeth (d) are about rectangular 
to the shaft (M); you may say: when the term patento-ternate is to 
be used. When ® is not much larger or much smaller than 90° (but 
1) Versuch einer spongiologischen Stenographie. In Tijdschr. Ned. Dierk. 
Vereeniging. V (1881). 
