204 AKT. 7. J. IJIMA : HEXACTJNELLIDA, IV. 



unpaired [)r()xiüial ray may l)e twice a« long as the paraiaugeiitials 

 ill the same .spicule. In most cases all the rays ure smooth 

 except for ;i s[)arse number oi' obsolete niicrotul)ercles near their 

 conically ])ointed or rouiiJed ti[)s. Howevei', some of the spicules 

 — without doubt those that are old and ready to be protruded 

 as })rostalia — show paratangentials which are entirely rough, this 

 being due to a thick covering of minute processes similar to those 

 I have observed on the corresponding spicules of Scyphidium 

 longlspina (PL II., fig. o). On the other hand, among those 

 pentactins already protruded fi'om the dermal surface as prostalia, 

 I find some with paratangentials roughened in the manner just 

 mentioned but others exhibit no trace whatever of such roughness. 

 Thus, it seems that this roughness may possibly never appear on 

 some of the pentactins, though under certain circumstances it 

 develops while the spicules are still hypodermally situated. 



The derinalia (PL VIII. , fig. 18) are generally stauractins ; 

 exceptionally pentactins. The former are nearly flat or just 

 perceptibly arched. The latter have the unpaired ray directed 

 ])roximad. The rays are strongly prickly all over, gradually 

 tapering from the base towards the pointed end. Length of 

 rays, 70-100// (on an average 8Ö/'-). Their average thickness 

 at base, /'. The arrangement of the spicules in their relation 

 to one another is rather irregular (see PL VIII., fig. 24), though 

 here and there an approacli towards forming (j[uadrate meshes is 

 observable. 



The fjadralla (PL VI IL, fig. 19) ai-e hexaetins with rays 

 characterized similarly as in the dermalia. All the rays in the 

 spicule are generally about equally long, though sometimes the 



