5382 T. A. STEPHENSON 
Here the same characters as before go down the side of the 
table, but there are fewer to go above. And even without using 
the full number of combinations possible there is an empty 
square, no forms being yet described to fill it. Perhaps some 
will turn up, or perhaps it indicates that vesicles are structures 
not developed at stages of mesenterial evolution such as that 
represented by the Condylanthidae. 
The diagram representing evolution in this group, as far 
as one may understand it, and for comparison with that given 
on p. 504 in Part I, would be as below. More will be said 
about it in the evolutionary section of the paper. An ancestral 
Hoactiniia corresponding to the HKosagartia on the 
other line, may be imagined—a good deal like a Haleam- 
poides. 
oaclinia 
Condylanthidae Aliciidae 
Myona ithidae Actiniidae 
This diagram shows the Aliciidae and Phyllactidae as 
parallels, and involves the assumption that they arose indepen- 
dently from the main line, as some of them at any rate may 
probably enough have done. If they had a common origin 
among the pre-Actinuds, and the Phyllactids changed their 
mesenterial arrangement afterwards, or if some Phyllactids 
arose from early Actinud forms and others from Alicud forms, 
that would modify the diagram, but it is all speculation. 
Further details about it will be found under Phyllactidae in 
Part IIT. 
