184 
ment in their organisation. In the textfigure 10 1 have given a 
diagram of the arrangement of the mesenteries. By means of the 
diagnosis and the textfigure it is 
easy to form an opinion of the 
length of the mesenteries and 
the arrangement of the different 
parts of the filaments. 
The two dissected specimens 
however differ in some points. 
The hyposulcus was, especially 
in the not reproduced specimen, 
very short, probably- owing to a 
strong contraction in this part. 
The filaments on the pa-mesent- 
eries were unequally developed 
in both specimens. In one of 
the two (textfig. 10) the filaments 
agree with those in the m-mesent- 
eries, the cnidoglandular tract was 
however very small but distinet. 
In the other specimen the fila¬ 
ments of the left pa were not 
well developed and only a little 
folded without bunches and dis¬ 
tinet cnidoglandular tract (I have 
howevernot sectioned this mesent- 
ery). The right pa formed a very 
long folded projection one side 
of which was furnished with cil- 
iated tract and scattered low cras- 
pedonemes, the other with a weak 
cnidoglandular tract. This latter 
specimen showed thus a some- 
what anormal structure of the pa- 
Fig. 10. Pachycerianthus plicatus. Diagram 
of the arrangement of the mesenteries. 
filaments. On the reproduced specimen (textfig. 10) there were no 
bunches of the ciliated tract in the undermost part of the Mi- 
filaments, but in the other specimen bunches agreeing with those 
on the other M-mesenteries were present. The arrangement of the 
