84 REV. E. o'meaiIa. 



Smith exhibits on one side of the central nodule a group of 

 four or five separate depressions which do not occur on the 

 other side ; and this is a regular occurrence. Besides, the 

 median lines at the central nodule and the under end-nodule 

 bend toward the same side — namely, that in which the above- 

 mentioned depressions occur, and which are situated in a 

 well-defined area. At the upper-end nodule the median line 

 at first takes the same bend as at the other nodules, but 

 afterwards changes round to the opposite side, towards a 

 small space in which no depressions occur. These peculiari- 

 ties render manifest the unsymmetrical character of the 

 valves. In many specimens the median line is bowed, how- 

 ever slightly, so as to present its concave side to the group 

 of depressions. In addition it is important to observe that 

 where these depressions lie to the right on the upper valve, 

 they are found also on the right in the underlying valve. 

 So that the GojnjjJionemecB are not diagonally constructed as 

 the Pinnularia are, but unsymmetrically on the homologous 

 sides, like Anomoeoneis and the Cynibellea. The structure 

 of the primordial cell corresponds : there is but one plasm- 

 band situated on the cell wall ; only one endochrome-plate 

 occurs ; but Avhile the former and the middle of the latter in 

 the CymbellecB lie on the more strongly-arched, we find them 

 in the somewhat unsymmetrical Gomphonemea {e.g., in Sphe- 

 nella vulgaris) on the less convex girdle -band. The central 

 plasm-mass is not so broad on the one side as it is on the 

 other, on which lies the nucleus and the turned -up edges 

 of the endochrome-plate, this is also the case in the greater 

 number of the Cymbellece. The endochrome-plate has the same 

 structure as in the last named, although its position differs to 

 the extent of 180 degrees. The division of the endochrome- 

 plate proceeds by an incision from the ends. The free edge 

 grows across the valve until the original position has been 

 reached. A transverse section of the Gomphonema- cell 

 would more clearly represent the relative position of the parts. 

 The genera Gomphonema and Sphenella are distinguished 

 from one another only by the circumstance that the frustules 

 in the former are stipitate, and non-stipitate in the latter, 

 which Pfitzer, following Grunow and Rabenhorst, considers 

 an inadequate generic distinction, for this reason, that the 

 stipitate forms occur free and with active motion. As respect 

 the substance of the stipes, it appears in this instance, as in 

 the case of Cocconema and Brebissonia, in its early stage as 

 a simple, colourless, well-defined gelatinous band ; but in its 

 more advanced stage of growth it presents a brownish central 

 thread, surrounded by a broad, colourless investment. 



