REPORT ON THE TETRACTINELLIDA. 
Ixiii 
The Dragmas. 
These spicules, which are secreted several together in the same scleroblast, are placed 
as an appendix to the microscleres which are secreted each in a single scleroblast, since 
they do not differ from them in form, and it would be cumbrous to subdivide the 
microscleres into two groups, say the monogennema and syngennema. 
1. Sigmadragma. — A sheaf of sigmaspires. 
2. Toxadragma. — A sheaf of toxaspires. 
3. Orthodragma (Fig. XIL, j). — A sheaf of straight trichodal rods (PL XVIII. fig. 13). 
In describing Dragmastra (Stelletta) normani, I used the term trichite-sheaves for these 
spicules. The term trichite may be retained to denote the individual hair-like rods of 
which the sheaf is composed. “ Trichodal ” will be used as an adjective to denote excep- 
tional tenuity. 
Series II. Asters. 
Section (a) Streptasters. 
The asters are divided into two subsections, the true asters or euasters, and the 
streptasters or those in which the actines do not proceed from a centre, but from a 
longer or shorter axis, which is usually spiral. 
1. Spiraster (Fig. XIL, s). — A spire of one or more turns, produced on the outer side 
into several spines. 
2. Metaster (Fig. XIL, u ). — A spire of less than a single revolution, with fewer but 
relatively longer spines than the spiraster. The spire sometimes has the appearance of a 
straight rod ; this may be due to the aspect in which it is presented, and to the fact that 
it does not make a whole revolution. It forms a link between the spiraster and the next 
form — the plesiaster. 
3. Plesiaster (Fig. XIL, v, tv). — The spines, or as they may now be termed, actines, 
proceed from a very short straight axis, so that they almost appear to radiate from a 
common centre. In forms with less than four actines no axis as a rule is discoverable, 
and the actines may actually proceed from a centre ; in those with more than three, the 
axis can always be made out, though in certain positions of the spicule it appears as 
though all the actines proceeded from a centre except one, which proceeds from one of 
the actines arising at a little distance from the common origin ; in this case the part 
of the actine which extends between the common centre and the origin of the excentric 
actine represents the axis. The plesiasters are always much larger w^hen fully grown 
than the metasters, with which they are associated, and the metasters are larger than the 
spirasters ; the three forms present a perfect gradational series, so that it is frequently 
