ON THE DEVELOPMENT OF LICHENOPORA VERRUOARIA. 93 
likely that any such exist. The view which seems to me to be 
suggested by my observations and by those of previous workers 
is that the basal lamina is the outermost layer of the body- 
wall; that the body-cavity it encloses has been repeatedly 
subdivided by the ingrowth of a series of branching and 
anastomosing ridges or septa from the body-wall. The whole 
upper surface of a Lichenopora colony thus corresponds with 
what would be seen in an end view of a growing point of 
Crisia. But whilst in the latter the growing edge is sub- 
divided by a very simple set of septa, which result in the 
formation of only two series of zocecia, that of Lichenopora 
is divided by an immensely complicated series of septa. The 
parallel is not, however, quite accurate ; since in Crisia, as in 
Tubulipora (cf. p. 81), the septa reach the growing edge of 
the colony, and the mature zoccia are thus completely outside 
the “ growing-point,” because part of the growing edge is used 
up in toto in the formation of each zocecium. The morphology 
of the Lichenopora colony can be most easily understood by 
considering a young colony like fig. 3. It will then be seen 
that while the lateral body-wall is complete from the beginning, 
the mouth of the expanded funnel is closed by a living body- 
wall. While this is constantly encroached on and altered by 
the formation of septa, whether those giving rise to new 
zocecia or those which form alveoli cr cancelli, the body-wall 
is never completely calcified in this region. For this uncalcified 
body-wall, which closes the mouth of the funnel-shaped colony 
of Lichenopora, of the growing points of Crisia, &c., the 
name “terminal membrane” may be suggested. It is this 
layer which gives rise to the polypide-buds, and is invaginated 
into the orifice of every zocecium. 
If the septa are really, as there seems every reason to believe, 
derivatives of the basal lamina, there is no reason for not re- 
garding them as ingrowths of a true calcified ectocyst; and 
they may accordingly be compared, in a general way, with the 
septa of a Coral (as already pointed out), or with the chiti- 
nous ingrowths which form the endoskeleton of a crayfish. 
