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POPULAR SCIENCE REVIEW. 
of M. Claparede (“Monatsb.” 1856, p. 500) and which is generally 
identical in all its characters with the Acanthodesmia,oi Johannes 
Muller (1858), we have the connecting link between the sili- 
ceous structure in this Order and some of the numerous aberrant 
varieties of the siliceous framework of the Polycystina. In 
this family the shell is very rarely symmetrical in any of its 
aspects, being formed (as seen in Fig. 6) of three or more 
straight or branching, and sometimes very bizarre- looking 
siliceous rods or bars, united together at one or more points, so 
as to form a solid piece. Within the rude cavity thus formed, 
the bulk of the sarcode body is sustained, a delicate investing 
layer being, however, as in the former case, extended exteriorly 
over the framework. Nucleus and sarcoblasts as described in the 
general characters of the order. To this family will be found to 
belong those strikingly curious forms in which the tendency to 
unsymmetrical growth attains the greatest limit, and which are 
known under the names of Dictyospyris , Stephanolithis , Glado - 
coccus , Stylocyclia, and Acanthodesmia. 
In the Acanthometrina there exists a much more complex, 
generally perfectly symmetrical, and beautiful arrangement of 
the siliceous skeleton, which in all the true Acanthometrce con- 
sists of a varying number of radiating spicules, disposed in 
pairs, and uniting at the central axis of the structure merely by 
close juxtaposition of their conical-shaped bases. Occasionally 
the spines are blade or oar-like — occasionally furnished with hilt- 
like processes placed at some little distance from their axial 
point of union ; and when these processes so far extend them- 
selves as to coalesce with those of the spicules next to them, 
they form perforated chambers often resembling those of some 
of the Poly cystine Haliommata . The nuclear mass is, in the 
Acanthometrce, not enclosed within a mere membranous chamber, 
but around the point of junction of the spines, which it accord- 
ingly more or less completely embraces and conceals. In the 
very early stage of Acanthometrce, the development of the 
spines takes place at the central point of the sarcoblast, and the 
spines as they grow gradually push the investing nuclear cap- 
sule (which is also developed in a very distinct form at this 
early period of the organism’s history), before them, just as the 
finger may push before it a glove-like process of thin india- 
rubber. In all probability the spines, after a certain time, cause 
the rupture of the nuclear capsule, which causes it to hang 
from their extremities in curtain-like festoons. It is extremely 
tough, however, and so hyaline that the structure within, until 
the nuclear mass is reached, is plainly visible. The sarcoblasts 
are, apparently, not quite so numerous in the Acanthometrce as 
in the Foraminifera and Polycystina . But in all other 
respects they are identical. 
