198 
Slipper Islands and one from Port Jackson and in both the sphincter 
shows the same structure. In the textfig. 14 I have reproduced the 
sphincter from the Port Jackson specimen. The ectodermal longi¬ 
tudinal muscles of the tentacles are ordinarily developed (Stuckey 
says: very strong) and form palissade-like close folds. The radial 
muscles of the oral disc are stronger than the longitudinal muscles 
of the tentacles between the insertions of the mesenteries, at the 
insertions of the mesenteries weaker. I have not observed any 
anastomoses between the muscle folds. 
The pairs of mesenteries vary in number. Stuckey States 
that the normal number appears to be 48 pairs, in one specimen 
he observed 56 pairs. As the number of mesenteries here agrees 
with that of the tentacles it should thus be 200 or more, if the 
statement of Stuckey is correct. In the specimen with 114 ten¬ 
tacles and 57 pairs of mesenteries there were 11, 9, 7, 7, 9, 8 
pairs of younger mesenteries in the compartments between the 6 
first pairs, counted from the one directive pair, in the specimen 
with 144 tentacles and 72 pairs 14, 8, 11, 10, 8, 15. The develop- 
ment of the mesenteries in the different compartments thus was 
irregular, in some compartments richer than in others. There were 
always two pairs of directives. In the large specimens the mesen¬ 
teries of the first, second, third, and part of the fourth were perfect, 
