RESTITUTION-BODIES AND FREE TISSUE-CULTURE IN SYCON 805 
drawn to a larger seale than figs. 7, a and b). It is possible 
that the abnormal-shaped Olynthi were produced by dermal 
blow-outs of the types of fig. 12, or by coalesced masses of 
irregular shape. 
Numerous other masses, however, were seen of the type 
shown in fig. 8. Here spicule formation had progressed well, 
but no osculum was present. The most noticeable point was 
the restriction of the gastral layer to part of the sphere (as 
already seen, e.g. in fig. 13). The gastral layer was usually 
one cell-layer in thickness, but in some masses was several layers 
thick at certain spots only (fig. 8). 
The disproportionate number of dermal cells had certainly 
delayed development. As I had to leave Plymouth the day 
after discovering this type of regenerate, their fate could not 
be ascertained. 
5. DARK-CENTRED MAssEs. 
These were both seen at Wood’s Hole and at Plymouth. 
Typically (fig. 11), they consisted of a dermal epithelium, 
surrounding several layers of pale cells, apparently choanocytes, 
which in their turn surrounded a central mass of dark yellowish- 
brown material, whose cellular nature could not be seen in 
vivo. The central mass is separated from the pale cells by 
a space. In one or two cases the central body was seen to be 
revolving. If this was so, then the collar-cells must have 
developed flagella on their inner side. 
The meaning of these masses is obscure. There is a strong 
resemblance between the inner mass and the yellow-brown 
masses seen in the subdivided spherules (fig. 5), and some 
resemblance also between the intermediate pale layer and the 
isolated cells of fig. 5. 
A few specimens were observed where a dark central mass 
was present, together with active choanocyte epithelium on the 
outside. 
6. ADHERENCE OF LARVAE TO Masszs. 
Both at Wood’s Hole and at Plymouth it was noticed that 
when cultures were made from sponges containing nearly 
