632 EDWARD POTTS. 



whatever we may believe as to the origin of Liranocodium 

 sowerbii, it is hardly possible to doubt that Limuocnida 

 tauganyicae and M. ryderi are native to the districts iu 

 which they have been found, and that, unless or until the 

 polyps of Bourne and Parsons have been seen to produce 

 the Liranocodium, it is quite within the limit of possibility to 

 suppose that they have had their origin in the Thames, or 

 from any other source from which the tanks in which they 

 were found may have been filled. 



EXPLANATION OF PLATES 35 and 3G, 



Illustrating Mr. Edward Potts' paper, " Oa the Medusa of 

 Microhydra ryderi, and on the Known Forms of 

 Medusae inhabiting Fresh Water." 



PLATE 35. 



Fig. 1. — Diagrammatic section of a terminal medusa-bud of the liydroid 

 colony of Limnocodium sowerbii. After Fowler, ' Quart. Jourii. Micr. 

 Sci./vol. 30, 1890, PI. 32, fig. 8. 



Fig. 2. — Portion of hydroid colony of Limnocodium sowerbii. After 

 Fowler, loc. cit., PI. 32, fig. 2. 



Fig. 3.^Hydroid form of Limnocodium sowerbii upon roots of pond- 

 weed. After Bourne, 'Proc. Roy. Soc.,' xxxviii, 1884, jt. 10. 



Fig. 4. — Portion of one of the hydroids of Fig. 3 seen in optical section. 

 After Bourne, loc. cit., p. 10. 



Fig. 5. — Limnocodium sowerbii, as seen floating. After Lankcster, 

 'Quart. Journ. Micr. Sci.,' vol. 20, 1880, p. 357. 



Fig. 6. — Limnocodium. After Allman, 'Journ. Linn. Soc.,' "Zool.," 

 XV, 1880, p. 134. X S. 



Fios. 7 and 8. — Two views of an embryo medusa of Limnocodium 

 sowerbii. After Lankcster, 'Quart. Journ. Micr. Sci.,' vol. 21, 1881, 

 PI. 13, figs. 4 and 1. 



Figs. 9, 10, and 11. — Hydroid figured by Parsons, ' Journ. Quek. Micro. 

 Club,' ser. 2, vol. ii, PI. G, p. 130. 



