214 J. MURRAY ON PHILODINA MACROSTYLA, EHR., 



drawn into it. When fully extended the tip forms a hemispheri- 

 cal prominence, still slightly inverted at the base. 



The lamellae (Figs. 19-20) are very large. They appear as 

 two plates, soldered in the middle line, and the common plate 

 thus formed standing forward as a flange, and at the extremity 

 bent forwards as a kind of beak (Fig. 20). Laterally the 

 lamellae extend far round, forming a kind of collar, diminishing 

 forward (as shown in Fig. 20), unlike most ordinary Philodinadae. 



The brush of cilia covers the whole tip. The cilia, of which it 

 is composed, act in concert, with a kind of automatic vibratory 

 motion, like those of the discs. 



The straight setae spring from the tip, close to the base of 

 the lamellae. They radiate from the tip, close under the lamellae, 

 and are distinguished from those of the brush mainly by tho 

 absence of motion. In these viviparous Philodinae they rarely 

 project beyond the lamellae, and are thus very difficult to detect. 

 In most other Philodinae they are better developed. 



The tactile setae are more conspicuous in this group than in 

 any other Bdelloids which I have studied. There are four, 

 two on each side of the tip. The two setae of each pair are- 

 close together at the base, and spring from the tip, close to 

 the lamellae. They are thick, long, tapering, and undulate. 

 They are put out as feelers before the tip is everted, and their 

 movements do not appear automatic like those of the brush,, 

 but intelligent. 



The antenna is a highly-developed organ, and conspicuously 

 differs from that of other Bdelloids. It is apparently three- 

 jointed or obscurely four-jointed, tapering from the base to 

 the beginning of the last joint, which is expanded at the tip 

 into a three-lobed cup, in the centre of which is a clavate 

 process, from which groups of setae diverge (PI. 15, Fig. 7, 

 and PI. 17, Fig. 18). In side view the antenna has a curious 

 resemblance to a human arm, with bent elbow and clenched 

 fist (Fig. 7). The articulation is best studied in this view. There 

 is first the large short basal joint a, then a short joint b, at 

 the end of which is the elbow, then a long, tapering joint c, 

 small at the base and again slightly near the distal end ; 



