3o6 WILLIAM ARCHER. 



inner angles, tlie incisions not proceeding so far as to effect 

 a complete separation. There is thus now a highly complex 

 form produced : sixteen quadrate segments have resulted 

 from the formation of the primary and secondary sets of in- 

 cisions, and these are combined into one tablet by five points 

 of mutual union ; that is to say, the single median point of 

 union of the group of four primary segments, the result of 

 the first segmentation of the original quadrate cell, and the 

 four points of union of fow sets of four segments of the 

 primary segments, now having each attained the original 

 dimensions. The original quadrate cell has now become a 

 quadrate tablet of sixteen times its superficial dimensions, 

 composed of sixteen compartments, divided off by deep 

 incisions, three from each side of the tablet ; each of these 

 proceeding from the middle of each side to the centre is, of 

 course, cruciform, whilst the two others, reaching only to 

 the point of union of each of the secondary sets of segments, 

 are simple ; but all the cavities of all the compartments of 

 the tablet maintain, of course, a common intercommunication 

 at the before-mentioned five points of junction (fig. 6). Such 

 an example, indeed, as this calls to mind a door-key of many 

 wards^ if so homely an illustration be allowable. 



Nor does this appear to be all : judging from Reinsch's 

 figures ^ (see our figures 5 and 6, after Reinsch) , and from 

 just a single mention made in his explanation of the plate, a 

 further apparently singular characteristic appertains to this 

 most curiously complex form. It would appear that even at 

 a comparatively early period of the progress of growth of this 

 form, that is, in examples with only four primary incisions, a 

 foramen or aperture — an indubitable hole (" Loch ") — exists 

 right through and through the cell at the very centre of the 

 common point of union of the segments, or in a sixteen-seg- 

 mented tablet five such holes may present themselves. These 

 foramina are square, or rather the sides of the short tube thus 

 formed are somewhat convex inwardly, and thus the angles 

 acute. In one of Keinsch's figures (fig. 5) this ojDcning is 

 delineated with its angles towards the ends of the incisions, 

 and in another (of a sixteen- segmented tablet, fig. 6), the 

 sides of the opening are shown as towards the ends of the 

 incisions (the author does not himself refer to this difference) . 

 To judge from Keinsch's figures, these holes seem very re- 

 markable ; they are not holes in one side of the cell-wall, 

 which, as we know, can sometimes occur, as in cells of 

 Sphagnum-leaf, the openings in the oogonia of CEdogoniuni, 

 &c. &c., but they are holes, bored, as it were, clean through 

 ' Op. cit., t. ii, fig. 1, k, m. 



