223 
a transitory decamerous State may appear. (Compare besides the 
diagnosis). 
Anatomical description. I have not much to add to 
Stuckey’s and Stephenson’s descriptions of the anatomy. The 
structure of the column is well described by these authors. In 
the uppermost part of the column I have on sections observed 
endodermal bays extending into the mesogloea to about half its thick- 
ness and arranged in longitudinal lines in the endocoels, which 
are here considerably larger than the exocoels. If these bays have 
arisen by contraction or are present also in wholly expanded spec- 
Fig. 25. Epiactis Thompsoni. Transverse section of oral disc. 
imens I cannot decide. The structure of the sphincter varies. In 
one specimen the sphincter agrees mostly with that reproduced by 
Stephenson, the main lamella is, however, indistinct as in Stuc¬ 
key’s figure of the sphincter. Sections of the sphincter in another 
specimen showed fewer folds than in the sphincter previously re¬ 
produced, the main lamella is considerably stronger and in the 
distal part now divided in two branches, now thickened in the middle 
part, being here either more solid or more or less divided in meshes. 
Stuckey’s figure of the muscles in the tentacles agrees with the 
figures in my sections, only in the furrows the longitudinal muscle 
layer is weaker in my sections. Stuckey has certainly sectioned a 
very extended tentacle. The radial muscles of the oral disc agree with 
the longitudinal muscles of the tentacles (textfig. 25), they are weaker 
at the insertions of the mesenteries than between the insertions. 
The pairs of mesenteries were in the specimen with 96 tent¬ 
acles 48 (6 + 6+12 + 24), in a specimen with 82 tentacles 41 
(6 + 6+12+16+1). In the latter the mesenteries of the fourth 
cycles are missing in several exocoels, one pair of a fifth cycle 
