SCOTTISH ROTIFERS, COLLECTED BY THE LAKE SURVEY. 197 



feeding has prevented a fuller study of the rostral processes ; hut I have thought at 

 times I could detect long setae, or pencils of setae, projecting laterally from the lamellae, 

 as in C. ehrenhergi, Janson (4). 



Vibratile tags. — These are of the usual narrow form. I have not been able to 

 count more than four pairs. 



Alimentary canal. — The jaws, stomach, and intestine are normal. There are two 

 teeth in each jaw, and the usual fine striae. The food is not moulded into pellets. 



Rump. — The preanal and anal segments, which form the rump, are but slightly 

 separated ; but the second constriction mentioned by Bryce doubtless marks the 

 separation, and the hood with its processes will then belong to the anal segment. The 

 two lobes which project from the end of the anal segment are thin hyaline flanges. 



Foot of four joints, short. Spurs rather long for a Calliclina of the central group, 

 narrow, tapering, slightly acuminate, obtuse, close together at base, but small interspace 

 showing in some positions. Toes very short, difficult to see, as the last portion of the 

 step is very rapidly made. 



Variations of C. plicata. 



Head. — The processes of the upper lip, which usually meet in the middle line 

 (fig. 14), are sometimes separated by a small but deep sulcus. A ligule is very 

 commonly present, in examples otherwise typical (see dotted line between the discs in 

 fig. 15). In its greatest development this is a drop-shaped body, apparently just 

 touching the head, a little to the ventral side of pedicels. 



Foot. — The first foot-joint sometimes has a boss, which may be centrally placed, as 

 in most species having this process, or at the posterior edge of the segment, as in 

 C. symbiotica. In an Indian form, not otherwise peculiar, this becomes a transverse 

 ridge, with a sharp edge. 



Rump. — Bryce does not refer to the processes on the posterior margin of the hood, 

 but his figure shows them. 



Their commonest form is shown (in fig. 14). A form in which they are quite 

 obsolete is figured (fig. 19). The posterior part of the hood is divided into three plane 

 surfaces, a central one and two lateral flaps. 



The processes are, on the other hand, often produced much more than in that 

 figured (fig. 14), and become in some forms very prominent. They are still, however, 

 quite rigid outgrowths of the skin, and do not appear to be articulated at the base. 



A form in which the development of these processes is carried still further is 

 regarded as being a stable variety, and is described below. 



C. plicata, Bryce, var. hirundinella, var. nov. (Plate II. figs. 16 to 18). 



Distinctive characters. — The processes on the anal segment are produced into long 

 ligular bands with rounded ends. They normally diverge widely, but they are 

 distinctly articulated at the base, and can be approximated, or even crossed over one 



TRANS. ROY. SOC. EDIN., VOL. XLVI. PART I. (NO. 7). 28 



