542 B. T. GUNTHER. 



of granular cell-substance may be seen radiating from the 

 nucleus, but the whole cell body otherwise has been meta- 

 morphosed into a homogeneous cartilaginoid substance. There 

 is no continuous lumen, although the cells are disposed in a 

 single series around the axis of the tentacle, and leave, on 

 shrinking, a small space where their adaxial surfaces should 

 come into contact. This potential lumen appears not to be 

 continuous even in the specimens treated with reagents, and in 

 living specimens it has no existence." 



In all the individuals which I have hitherto examined the 

 larger and older tentacles were always hollow throughout their 

 length (PI. 40, figs. 2 and 5), and it is only to the younger 

 and smaller ones that the above-quoted descriptions of Allraan 

 and Lankester can apply. Moreover, in a considerable number 

 of sections of tentacles examined, the lumen of the tentacles 

 was found to be directly continuous with the lumen of the 

 ring canal, and the endodermic lining of the tentacle was 

 directly continuous with that of the ring canal as seen in 

 section in PI. 40, fig. 2. 



From this it appears that the tentacles of Limnocodium are, 

 morphologically speaking, hollow tentacles, though it is 

 quite possible that under certain circumstances they often 

 contract to such an extent that the lumen vanishes. An 

 indication of this contractile power is afi'orded by the exist- 

 ence of a powerful circular muscular coat at the bases of 

 the ectodermal cells. In obliquely cut sections such as the 

 one figured in PI. 40, fig. 5 a, these circular muscles may be 

 seen at the two ends of the section as transverse lines (circ. m.). 



The endodermal lining of the tentacles consists of very large 

 clearish cells very similar to those of the tentacles of Limnoc- 

 nida. Their contents are very probably of a gelatinous nature, 

 which gives the tentacles a certain amount of firmness. 



Nervous System. — The nerve-ring lies on the inner or 

 subumbrellar side of the circular canal at the attachment of 

 the velum. It is seen in transverse section in PI. 40, figs. 2 

 and 3. The nerve-fibres composing the ring, as in other 

 medusae, are divided into two bundles separated by the sup- 



