Misdirected Efforts to Conjugation in Spirogyra. 207 



existence it was a free floating organism, drifting at the mercy 

 of the winds and currents. All these circumstances conspire 

 to render the Graptolite one of the most suitable of fossils for 

 the purposes of the working geologist and systematist ; its 

 short vertical range affording elements for the subdivision of 

 the accepted Lower Palaaozoic formations into their component 

 zones ; its wide horizontal distribution allowing of the exact 

 parallelism of synchronous deposits in areas nowgeographically 

 separated ; and its universal dissemination rendering it easy of 

 collection and study. 



CORRECTIONS. 



Vol. iii. page 253. The reference in the third note (J) should be transferred 



from Retiolites to Didymogruptm. 

 Vol. iii. page 455, Table I. For (a) Lower Ludlow read (a) Upper 



Ludlow. The " Calciferous Group " should be united with the 



" Potsdam Group " in the Cambrian. 

 Vol. v. page 278, line 14 from the bottom of page, for Tetragraptus read 



Tngonograptus. 

 Vol. vi. page 19, line 12 from the bottom of page. D. vacillans, Tullb., is 



a Lower-Arenig species. 



XXVI. — On Misdirected Efforts to Conjugation in Spirogyra. 

 By H. J. Carter, F.R.S. &c. 



[Plate XIV. A. figs. 1-3.] 



Turning over the leaves of a MS. microscopical journal 

 which I have kept since 1854, I observed figures of Spirogyra 

 endeavouring to conjugate with Cladophora ; and not being 

 aware that any such fact has ever been published or even al- 

 luded to, it seems to me desirable that it should be publicly 

 recorded. The material in which it occurred was obtained from 

 a freshwater pool in the marshes of the island of Bombay, in 

 the month of March 1854; and all that I can state respecting 

 the species of the filamentous Algee concerned is, that the 

 Spirogyra was " double-banded," and the Cladophora the 

 species usually found iu the neighbourhood ? tranquebariensis. 

 Kg. Accompanying the figures, however, is the following 

 note, viz. : — 



" Figs. 5, 6, 10, 11, and 12. Spirogyra trying to conju- 

 gate with Cladophora, in which the contents of the cell of the 

 former are passing off into long root-like processes of cell- 

 membrane applied to a filament of the latter. This was a 

 frequent occurrence in a large basin of water wherein the 

 Spirogyra and Cladophora^ among other things, happened 



15* 



