( 110 ) 
Scnurze & LENDENFELD (1889 p. 8) have about the same conception 
of the spiculum: “gestreckter Aster; ein Schaft, von dessen beiden Enden 
Strahlen abgehen.” Comparing now the three quoted illustrations, it 
becomes evident that there are important differences between them. 
Notwithstanding Scnvrze & LENDENFELD illustrate a spicule with a 
long “Schaft” and long pointed “Strahlen”, we find in the definition 
of LenpenreLpD (1890, p. 419) that the amphiaster is: „ein in die 
Lange gezogener Stern, die aus einem Aurzen, geraden Schaft besteht, 
von dessen Enden mehrere /urze Strahlen abgehen”. Indeed: tot 
capita tot sensus. If, therefore, I bring certain amphiasters to the 
spinispirae, only such are meant as Sous describes e. g. in Séryphnus 
niger. 
Carter (1879 a, p. 354—357) has introduced the term “spinispirula” 
for spiniferous spirally twisted spicules.” Such spicula are, according 
to CARTER exceedingly polymorph. They may be “long and thin” or 
“short and thick”. The spines may be “long and thin... or long 
and thick... or obtuse... The spines may be arranged on the spicule 
in a spiral line, corresponding with that of the shaft... or they may ~ 
be scattered over the shaft less regularly... Lastly, the shaft may 
consist of many or be reduced to one spiral bend only...” 
Instead of chosing one of the various terms mentioned above, I 
prefer the new term spinispira, which is then simply: a spined 
a-spiraxon. If in future it happens become to a desideratum to have 
more than one name for such spicula, one might distinguish two 
groups of spinispirae, viz. forms with long spines and such in which 
the spines are small, in comparison to the total length of the spiculum. 
In the former group the ratio between the length of the spines and 
the total length is usually no more than 1:38; very seldom as much 
as 1:7; the number of revolutions is generally not more than 17/,. 
In the latter group this ratio is usually at least 1:10; the number 
of revolutions as a rule more than two. 
4. Microspira. 
In some sponges very minute spicula occur, especially in the super- 
ficial (dermal) layers and lining the canals, which are either distinct 
a-spiraxons, or modifications by reduction. For obvious reasons it can 
only be made out with a microscope of very high power and in favourable 
situation in the preparation, whether they are smooth or minutely 
spined. In such small spicula it is not always possible to distinguish 
with certainty whether they -are minute spinispirae, sigmaspirae or 
spirulae. Moreover they show generally manifold transitions in one 
and the same sponge specimen. This is e.g. the case in Placospongia 
