210 DITBLIN NATTRAL HISTOEY SOCIETY. 



and spinous. My friend, Mr. Edward Crowe, lately showed me speci- 

 mens of Zygnema, in which the entire cell-contents of many joints of the 

 filaments had become consolidated into a globose or somewhat pear-shaped 

 and smooth spore-like body, which, by expansion in one direction 

 towards one side, eventually burst through the boundary- wall, emerg- 

 ing into the surrounding water by the rupture thus effected. Mr. Crowe 

 informs me that he was not able to trace their ultimate destiny, as they 

 indeed perished before undergoing any further development. It is pro- 

 bable that these bodies, both in the Desmidians to which I have above 

 alluded, as well as the similar productions in the above-mentioned Zyg- 

 nemacse, in each case formed without conjugation, are Gonidia, by which 

 the organisms may be severally propagated. It may not be out of place 

 to mention here that I have several times noticed in Closterium lunula 

 the entire cell-contents transformed into a dense longitudinal series of 

 flask-shaped bodies, with their narrow necks projecting to the outer 

 wall, j)recisely similar to those figured by Carter (''Annals of JS'atural 

 History," 2nd series, vol. xvii., p. 114, Plate IX., Fig. 9), as occurring 

 in Spirogyra, also by Henfrey (''Quart. Journ. Mic. Sci.," vol. vii., p. 27, 

 PI. III., Fig. 12), as occurring in his Chlorosphcera Oliveri, equivalent, 

 I think, to Eremosphoera viridis (de Bary) ; and I imagine also the same 

 as the unicellular alga mentioned by Hofmeister in his paper " On the 

 Reproduction of the Desmidiae and Diatomeae," translated in " Annals of 

 Natural History" (vol. i., 3rd series, p. 1, January, 1858). In my spe- 

 cimens of Closterium lunula alluded to, the longitudinal mass of these 

 flask-shaped bodies more than once has suggested to me the hanks of 

 onions as seen hanging up in the market. I have never seen them, 

 however, to produce what Professor Henfrey considered the spermato- 

 zoids in his Chlorosphaera, which plant, as I have before elsewhere stated 

 ("Natural History Eeview," vol. v., p. 258), though then without know- 

 ing that De Bary and Henfrey had named it, is of common occurrence in 

 our district. Another curious growth in the interior of Closterium lunula 

 I would just notice. I refer to the production, within the otherwise 

 empty frond, of a slender jointed filament, contorted and twisted in 

 every direction, and occasionally inosculating ; the joints without any 

 apparent contents, save a very few green granules, scattered at conside- 

 rable intervals. This I should imagine a parasitic growth, possibly at 

 the expense of the original cell contents, though it is questionable how 

 the germ could find an entrance into the apparently uninjured ceU. Such 

 I also thought the flask-shaped bodies above mentioned, until I met with 

 Professor Henfrey' s remarks on the phenomenon in Chlorosphaera, nor 

 does it quite appear that his conjecture is altogether proven. 



Before attempting, in a measure, to account for the above described 

 curious external aberrations from the normal form, it will, I think, be 

 well briefly to draw attention to the mode of division in this family of 

 Desmidiaceae. So far as I can make out, there can be little doubt that 

 in these plants the first step in the process of division is the formation 

 of a septum at the central space or isthmus, whereupon the segments 

 become gradually removed more distant from each other by the growth 



