44 Mr. K. Vullcntiu o/t the 



The structure of a flame-cell or vibratile tag is found to 

 alter in appearance from wliiclicver point it is observed. 



Is there a single cilium within the tag, or are there minute 

 cilia, as suggested by Dr. Moxon, '' on each inner broad surface 

 of the tag " ? 



" The next point," says Dr. Hudson, " is whether these 

 tags are opened or closed at their free ends." 



Mr, Jackson, in his edition of liolleston's ' Forms of 

 Animal Life,' says : — " They [the lateral canals] carry a 

 number of ciliated organs, each of which consists of a pyri- 

 form canalicule, lodging at its free broad end a flame-cell. 

 The canalicule is closed (Plate) or has a lateral aperture 

 (Echestein)." 



It seemed to me hopeless to attempt to arrive at any satis- 

 factory conclusions concerning the structure of a flame-cell 

 by employing the same means as hitherto employed ; the 

 attack to be successful must be made from another quarter. 



Braclilonus ruhens is a very common Rotifer, and fortu- 

 nately possesses flame-cells of considerable dimensions. 

 After several failures I succeeded in preserving a gathering 

 of these Rotifers in a fairly expanded condition, and also in 

 cutting sections of them. In this species of Rotifer I find an 

 individual flame-cell to consist of a hyaline cylinder, the 

 extremity of wdiich is rounded and closed, a single cell 

 possessing a nucleus forming the distal termination. Springing 

 from the centre of this cell and projecting forwards to almost 

 the junction of the flame-cell with the lateral canal is a 

 tapering broad-edged cilium, which has a free motion in the 

 interior of the cell. The junction of the flame-cell with the 

 lateral canal is marked by a fine granular deposit on the walls 

 of the canal [vide PL V. fig. 14). 



Lateral Canals. 



The minute structure of these canals is a point to which 

 but little attention appears to have been hitherto directed. 

 The only reference which I can find relating to the minute 

 structure of these canals is by Mr. Jackson, lie says: 

 " These tubes [lateral canals] have nucleated walls and are 

 ])robably intracellular." The structure of tlicse canals is 

 most easily distinguishable in Laci'nulan'a social is. On refer- 

 ence to fig. 10 A, and the accompanying explanation, the 

 walls of the lateral canals are seen to be lined with large 

 cells, each cell being furnished with a distinct nucleus and 

 nucleolus. 



There is, however, one important jtortion of the lateral 



