Structure of Hologloea dubia. 407 



there are rounded lumps of gelatinous inaterial containing irregu- 

 larly arranged nuclei. A more or less definite line of nuclei (d) 

 appears to run along the closed end of the horseshoe, and then 

 on to the limb. The gejieral appearance gives the impression 

 that a proliferation of cells is taking place in the attached por- 

 tion, and in the neck region just alluded to, and that the cells 

 thus formed are wandering on to the limb.. If this be the case, 

 it is possible that the organ is of the nature of a stolon. 



General Remarks. — It appears to be impossible to indicate the 

 relationships of this curious organism. Tlie marginal bands at 

 first call to mind those of a ctenophoran, and the main central 

 and aboral canals in like manner suggest the stoniodaeal and in- 

 fundilnilai- canals respectively, but there is no trace whatever of 

 any structures resembling the canals that arise from the infundi- 

 bulum : there is no sense organ : no nerve system : no con- 

 tractile tissue ; the marginal bands are entirely deviod of cilia, 

 and if the deep groove has any relation to a tentacle sheath it is 

 reraaikaltle for its asymmetrical developint^nt. The total absence 

 of cells on the external surface is an extraordinary feature, nor 

 do the specimens convey the idea of this being due to accident 

 or bad state of preservation, as they are all in precisely the same 

 condition, and, moreover, the cells of the bands on the canal 

 wall and of the oral and aboral organs are all intact. 



Comparison with the members of any other group of animals 

 appears impossible, and the only hypothesis as to its significance 

 that I can offer is one that is suggested by the oral organ. In 

 connection with this I have described above what has the ap- 

 pearance of a proliferation of cells taking place on and close to 

 the part which is attached to the oral margin. From this part, 

 also, it looks very much as if the cells were passing off on to 

 the limb of the organ. If this be so, then it is possible that the 

 latter is an early stage in the development of a stolon, and 

 that this enigmatical organism is a nurse form in the life history 

 of some animal — but as to what this animal may be we have at 

 present not the slightest clue. 



