MATERIALS FOR A MONOGRAPH OF THE ASCONS. 3827 
structure. From appearances such as are figured in fig. 37, 
and which are frequently met with, the collar-cells of 
Leucosolenia would appear to divide longitudinally. 
VII. An ABNoRMAL TRIRADIATE. 
Fig. 101 on Pl. 20 represents part of an abnormal triradi- 
ate system of Clathrina coriacea with the cells upon it. 
This drawing was made by me more than ten years ago, but 
I have always kept it back in the hopes of finding other 
abnormal forms, and devoting a special memoir to them. As 
will be seen, one ray of the triradiate has two branches 
symmetrically placed on each side of the main shaft, each 
branch with a cell similar in appearance to a “thickener” 
attached to it. 
From a single observation of this kind it is difficult and 
unsafe to draw conclusions or to attempt to reconstruct the 
course of events. Did the founder and thickener go off in 
different directions? Or, after the founder had gone off, did 
the thickener divide into two and so produce two daughter 
rays? It is unfortunate that the spicule, having reached the 
limit, apparently, of its growth, does not furnish any answer 
to these queries. ‘I'wo things may be noted, however; one 
is that the three principal rays of the spicule are unusually 
stout and large, indicating great secretive activity on the 
part of the formative cells; the other point to be noted is 
that the two branch-rays are set on to the main ray at the 
same regular angle of 120°, which characterises the junction 
of the three principal rays. 
VIII. Some Osservations oF THE Disposirion OF THE T'rI- 
RADIATE Systems IN LEUCOSOLENIA LIEBERKUHNII. 
The observations to be recorded were made by me during 
my tenure of the Oxford Table in the Zoological Station at 
Naples during the year 1891-92. Leucosolenia lieber- 
kiihnii occurred then in the greatest abundance on the 
