228 
with 7 longitudinal ridges on each side of the directives. Both 
siphonoglyphes are of ordinary breadth and lack aboral prolong¬ 
ations. 
Anatomical description. The ectoderm of the column is 
rather high, but considerably thinner than the mesogloea. It con- 
tains numerous giand cells and nematocysts 17—24Xabout 1,5 
— almost 2,5 (-i. The cinclides seem to have arisen partly by in- 
31 
30 
Fig. 30, 31. Acraspedanthus elongatiis. Fig. 30. Transverse section of the outer part o£ 
the mesentery figured in fig. 28. Fig. 30. Transverse section of one mesentery of the 
second order. 
vaginations from the ectoderm, partly by evaginations from the 
endoderm. The circular muscles of the column are ordinarily devel- 
oped, on the other hånd, the mesogloeal sphincter is weak and 
situated close to the outer tentacles. It is mostly reticular, broader 
in the proximal part than in the distal, and wholly separated from 
the endodermal circular muscles. It stands nearer to the ectoderm 
than to the endoderm (textfig. 27). The ectoderm of the tentacles 
is high and contains numerous nematocysts 16— 27 x 1 , 5 — 2,5 /a 
(in four examined specimens 16—22 x 1,5 17—27 x 1,5 — almost 
2 jii, 17— 22 X 1,5 21—26X2 — 2,5 (. 1 ) and numerous spirocysts 
12 X almost 1 //—30X2,5 The longitudinal muscles of the tent- 
