88 AUCIIER AND DIXON, ON DESMIDIACEJS, 



a line with the lower older segment, and that projecting to 

 the left the same for the upper, by reason of the fresh acces- 

 sion to the mass of endochrome, with its central series of 

 corpuscles, being continued in an uninterrupted, curved man- 

 ner from each of the older segments into the new. But the 

 new laterally projecting segments do not in either instance 

 form an equally armed cross, for what is wanting in their 

 length as well as breadth, as compared with the old, goes to 

 make up a somewhat quadrate central inflation. Tetmemorus 

 not being a compressed form like Euastrum, there is not the 

 same opportunity for the change of plane of growth shown 

 by the case in that genus (fig. 12), but that the new growth 

 has assumed a slight twist, is shown by the different relative 

 positions of the terminal emarginations. 



The first figure of an abnormal Tetmemorus (fig. 11), 

 shows another state, though not bearing any connexion with 

 the curious aberration of the external form, and that is the 

 disposition of the cell-contents. The entire endochrome has 

 become transformed into four green and four brown bodies, 

 the latter the smaller, and smooth in outline. This, how- 

 ever, docs not appear to have any dependence on the externa] 

 abnormal condition, for I have frequently noticed the same 

 transformation of the cell-contents, especially in this species, 

 in the ordinary normally formed individual, as well as in 

 many other species — for instance, in Tet memorus /avis, Micros* 

 teriaa denticulata, Euastrum didelta, several Closteria, and 

 many others; and often to the entire absorption of the cell- 

 contents to produce these spore-like bodies. In Tetmemorus 

 Brebissoniil have seen from one to a dozen or soof these bodies, 

 more often four only, sometimes green, sometimes red, and 

 sometimes alternately red and green. I have not been able to 

 see any further development of those spore-like bodies. The 

 abnormal specimen from which the figure was taken 1 kept 

 on a slide moistened for many weeks, but no alteration look 

 place in this or any other respect, save that the red bodies, 

 from being undefined, grew more and more smooth in out- 

 line. These are, doubtless, similar productions to those 

 figured in the ' British Desmidieae/ pi. iv, fig./, as occur- 

 ring in Desmidium Swartzii. There, however, there is hut- 

 one spore-like body formed in each joint. 1 have myself 

 met with this species in the state so admirably figured in 

 Ralfs; and though I kept the specimens for some time living, 

 no further alteration took place beyond the decay of the old 

 filament; and the spore-like bodies themselves subsequently 

 perished. Bodies, which I suppose arc of a similar nature, 

 as is well known, are occasionally met with in species of 



