THE ROTIFERA OF THE SCOTTISH LOCHS. 167 
BDELLOIDA. 
Structure.—The details of structure given in a previous paper (39) may be here 
supplemented from later observations. 
Rostral jprocesses.—The rostrum of Bdelloids bears generally, and perhaps 
invariably, at least four different kinds of processes—the lamelle, the brush of cilia, 
straight sete radiating from the tip close under the lamelle, and some thicker tactile 
sete which arise singly or in pairs from about the centre of the base of each lamella. 
Most authors only mention the lamell and cilia, without discriminating the various 
kinds of cilia or set, Janson (24) states that towards the ventral side the cilia are 
elongated into ‘ Tastcilien’; Bryce (7) distinguishes between tactile and motile cilia, 
without entering into details; Wrser (52) only mentions the tuft of cilia, but he figures 
in Rotifer vulgaris two kinds of cilia—at each side a pencil of much longer cilia which 
probably correspond to the tactile sete. ZacHarras most clearly discriminates (55) the 
crown or tuft of cilia and the two long ‘Tasthaare.’ The straight radiating sete I do 
not find anywhere distinctly referred to. Most figures only show one kind of cilia, 
which may be the tuft or brush, but in many cases probably indicate the radiating sete. 
Rostral lamelle.—There is a consensus of opinion among authors, including such 
excellent observers as ZELINKA, JANSON, WEBER, and Bryce, that the rostral lamellee are 
two distinct plates, which in those species where they appear to form a single two-lobed 
hood are really overlapping at the bases. In deference to these authorities I refer to 
them as lamellze, although in many cases they seem to me to form a single organ. In 
microscopical matters it is especially necessary to avoid the bias of authority, and to 
describe things as they appear to us, as ZacHaRIAS pleads (55) when giving an unorthodox 
interpretation of the vibratile tags. I have never detected this overlapping of the 
lamellae. In many species—Cuallidina russeola, C. tetraodon, and C. plicata for common 
examples—the lamellee appear quite distinct and far apart. In most species studied by 
me they seem to form a single, more or less distinctly two-lobed hood. The meeting-point 
of the two lobes generally forms a prominent beak, pointing forwards. In the viviparous 
Philodinadee (P. macrostyla, etc., and the genus fotifer), the appearance gives some 
support to a suggestion made by Mr Bryce in a letter, that they are adnate (see 
Plate V. fig. 21). 
In a great many instances, when the lamellz are most fully extended, the two-lobed 
character disappears, and the organ appears as a simple hood, like that of Metopidia, 
Stephanops, or Diglena, merely curved forward at the tip (Plate I. fig. 89). 
The brush, or tuft or crown of cilia—Most conspicuous of the rostral cilia is 
usually the tuft. These cover most of the surface of the evertile tip, and are usually 
gathered together into a compact brush, which possesses an automatic motion similar 
to that of the wreaths, but less regular as to direction. By means of them many species 
can glide forward rapidly, thus supplementing the Bdelloid step. They probably also 
assist the wreaths, as they are often in active motion when the animal is feeding, 
TRANS. ROY. SOC. EDIN., VOL. XLV. PART I. (NO. 7). 23 
