DlTBLni KATUKAl HlflTOBT 80CIETT. 208 



the intervening growth has caused the old segments to become somewhat 

 twisted in regard to each other, and, as in the preceding instances in 

 Euastrum, it has assumed a direction at right angles to the axis of the 

 older segments. The last sketch (Fig. 15), which represents a second in- 

 stance met with by me of this phenomenon in the same species, shows 

 that the lateral extremity to the right is really what ought to have been 

 normally the new segment on a line with the lower older segment, and 

 that projecting to the left the same for the upper, by reason of the fresh 

 accession to the massof endochrome, with its central series of corpuscles, 

 being continued in an uninterrupted, curved manner 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 want- 

 ing 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 opportu- 

 nity 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. 14) 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, 

 however, does not appear to have any dependence on the external ab- 

 normal 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 

 Tetmemorus Icdvis, Micrasterias denttculata, Euasti-um didelta^ several 

 Closteria, and many others ; and often to the entire absorption of the 

 cell-contents to produce these spore-like bodies. In Tetmemorus Brehi^ 

 sonii I have seen from one to a dozen or so of these bodies, more oft^i 

 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 I kept on a slide moistened for many weeks, but no alteration 

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

 being undefined, grew more and more smooth in outline. These are, 

 doubtless, similar productions to those figured in the ** British Desmi- 

 dia)," Plate IV., Fig./, as occurring in Desmidium Stcart&ii, There, 

 however, there is but one spore- like body formed in each joint. I have 

 myself met with this species in the state so admirably figured in Rolfs ; 

 and though I kept the specimens for some time living, no further altera- 

 tion took place beyond the decay of the old filament ; and the spore- 

 like bodies themselves subsequently perished. Bodies, which I suppose 

 are of a similar nature, as is well known, are occasionally met with in 

 species of Spirogyra, and which, as here, not being the result of conju- 

 gation, are formed by either a portion or the whole of the green contents 

 of a single joint being absorbed in their production, and are spherical 



