CLASSIFICATION OF ACTINIARIA 5138 
perfect mesenteries, and no distinction of mesenteries into 
macro- and microcnemes. ‘The longitudinal mesenterial 
muscle consists typically of a feeble layer, not forming the 
sort of sheet or retractor characteristic of anemones. There 
are no basilar muscles, and directives may be present or not. 
The ectoderm of the body-wall may or may not contain a weak 
muscle-layer. The mesogloea is Madreporarian rather than 
Actinian. 
Text-fig. 4 shows the contrast between various sorts of 
Actinian mesenterial musculature and the sort of thing found 
in these ‘soft corals’. In the former there may be seen 
dendrites or processes projecting from the general mesogloea 
for the support of the muscle-fibres. In the soft corals the 
surface of the mesogloea is typically either straight or lobed 
as at p, but has a weak fringe of muscle-fibres directly upon it, 
not elevated on processes. The sort of thing is better seen in 
Text-fig 5. ‘Text-fig. 6 shows Discosomid sting-cells contrasted 
with typical Actinian sting-cells from acontia and acrorhagi, 
&e. The general difference in size between a and B (‘soft 
corals ’) and the others is very marked. c is unusually large 
for an Actinian cell, p and © providing more average examples. 
A Discosomid filament, showing the absence of ciliated tracts, 
is to be seen in Text-fig. 17, c. 
A microscopical study of a few of these forms at once suggests 
a difference from the anemone type running through the 
histology and other things. Even when anemones have 
weak musculature it has a different appearance. These are 
things which one cannot well bring out in figures without an 
extensive histological demonstration, but are easy to see in 
actual sections. The curiously feeble mesenterial musculature, 
the presence of very large sting-cells, the absence of ciliated 
tracts, the appearance of the mesogloea and cell-layers, the 
lack of siphonoglyphes, the tendency towards compound 
individuals and colonies, the weak or absent sphincters, and 
sometimes the strong permanent actinopharyngeal ridges and 
form of the tentacles, and so on, are points which, taken 
together, suggest Madreporaria, of some or all of which they 
