352 WILLIAM ARCHER. 



Braun), &c., for examples of very varied and at same time 

 seemingly characteristic outlines. 



But amongst unicellular plants belonging to the class 

 Phycochromacese, so frequently found in the same situations 

 associated Avith the foregoing, as well as Avitli other less pro- 

 minently marked chlorophyllaceous types, not until recently, 

 so far as I am aware, has attention been drawn to any ex- 

 amples of a specially figured outline — that is, as mentioned, 

 in shape otherwise than globulai-, ellipsoidal or cylindrical. 



I need hardly contend, indeed, that the " figure-of-8- 

 shape," assumed by many such during the progress of self- 

 division, cannot be regarded as an exception, or as in itself 

 special. Thus, in the genus Synechococcus (Nag.), for in- 

 stance, the ordinary oblong subcylindrical cell becomes trans- 

 versely constricted during growth, so as to assume a"figure- 

 of-8-shape ;" but the two segments having attained their full 

 size, the constriction is simultaneously carried through and 

 through, separation ensues, and the oblong subcylindrical 

 figure in each new cell is resumed. 



Possibly, indeed, the departure from the so frequent ellip- 

 soidal type, which is shown by the cuneate or rather obovate 

 cells of Gompliosphoiria aponina (Kiitzing), may, so far as it 

 goes, indicate a certain amount of approach to a special 

 figure, enhanced, too, as it might appear to be, by the very 

 pretty obcordate shape presented by the cells during division. 

 Indeed, a doubly obcordate figure is not unfrequently seen ; 

 that is, when the division proceeding vertically from above 

 downwards, being j)artially advanced, is quickly succeeded 

 by a second line of division setting in at right angles to the 

 former, also proceeding vertically from above downwards — 

 then the shape assumed presents an obcordate outline on 

 each of its four vertical aspects, and when viewed from above, 

 or somewhat obliquely, is seen to be four-lobed. A cell in 

 such a progressive stage of division is thus somcAvhat com- 

 parable to the figure of a four-lobed Euonymus fruit. (This 

 allusion, of course, is only to assist in conveying a concep- 

 tion of the shape presented.) But, when the self-division is 

 complete, the cuneate or obovate figure is resumed. Indeed, 

 even the regular tapering off tOAvards the lower or inner ex- 

 tremity of the cells may be possibly held to be but a conse- 

 quence of their mutually approximate radial dis^^osition, occur- 

 ring, as they do, imbedded in the substance of the ends of a 

 number of radially projected dichotomously subdivided arms 

 of rather firm gelatinous matter, emanating in a somewhat 

 stellate though quite irregular manner, from a common 

 centre, the Avhole surrounded by a more or less conspicuous 



