246 
iiiat the sections are made through the young top-parts of the colonies. However the inverted 
1 atio may also occui (. EucLfitip . plctnci^ . I he axial epitheha are very thin as to the ectoderm 
(3 12 fO except at the base of the spines, and as to the mesogloea (less than 1 to 7 T). 
The mesogloea is rarely thick, as in Schizop. affinis. The entoderm usually is thin, but in 
rare cases may attain a rather great thickness, up to 40 u.. 
GENERIC DIFFERENCES. 
Genei ally these differences are not very great, while often the differences in micros¬ 
copical anatomical structure within the same genus are as large or even larger than between 
two genera. Even within one and the same species the anatomy may vary exceedingly. The 
most striking is the absence ot an actinopharynx in the genus Sibopathes , which fact is accom¬ 
panied by a greater development of deeply staining glandcells in the entire entoderm of the 
oral cone, but also of the body wall, and even of the axial sheath, by the absence of mesen¬ 
terial filaments, and by 7 the very’ slight development of the mesenteries. — For the rest there 
may be given, properly speaking, no generic differences, except at the utmost that generally 
the development of the musclefibres is great in both sub-genera of the genus Cirripathes and 
that in this same genus the pigmentation of the actinopharyngeal ectoderm and of the mesen¬ 
terial filaments may be very copious. But even this can not be given as a rule, as is very 
apparent by comparing in this respect the various colonies of Stic hop. variabilis. 
