Folliculina holloni (S. Kent). 309 



at the same time the dorsal wall of the shell had been partially- 

 broken and opened, two loug pointed appendages were to be seen, 

 one pointing to the month and one to the accidentally opened 

 passage at the back ; and this latter prolongation was the longer 

 of the two, though belonging to the smaller of the lobes. 



The vibratile elements which run along the peristome are not 

 cilia, but membranellfe, or what we might with Mobius call 

 pectindlm, each of them consisting of half-a-dozen cilia. These 

 small groups of cilia are compressed into a lamina, whose basis 

 marks a transverse line on the peristome border, and these parallel 

 rod-like transverse lines give to the peristome border a special 

 scalariform appearance. 



The pectinellse, singly considered, possess at times an inde- 

 pendent activity. They may vibrate in one region of the peristome 

 and not in another ; but at other times all the pectinellse are seen 

 moving together, or the whole of them are turned from right to 

 left or from left to right ; this is, for instance, what happens when 

 the lobe expands. As long as it was still inside the shell, all the 

 pectinellse were facing towards the median line of the lobe, which 

 had the appearance of a horseshoe with inside denticulations 

 (fig. 3) ; but as soon as the lobe is expanded, the entire row of teeth 

 rapidly turns outside, describing an arc of 180°, with the result 

 that the horseshoe has all its teeth pointing towards the exterior 

 (fig. 1). At the same time it looks as if the pectinellse had grown 

 much longer ; perhaps, when looking towards the concavity of the 

 lobe, they were more or less curled downwards. 



The peristomial furrow, beginning on one side at the base of the 

 funnel, runs along the whole border of the lobes, descends to the 

 funnel again, and plunges into the vestibulum, reaching as far as 

 the mouth at the bottom of the vestibulum itself ; but the more it 

 descends the thinner are the pectinellffi, and at last we find 

 nothing but ordinary cilia. These, however, do not lose their 

 activity, but on the contrary show more rapid vibrations, and near 

 the bottom of the vestibulum the movements are so quick that one 

 might be tempted to see there an undulating membrane. 



The body of Folliculina is covered all over with cilia, disposed 

 along longitudinal grooves or striae (about 2^ yu distant from each 

 other), which can be followed from the tip of the lobes to the 

 posterior extremity. When seen along the line of its longitudinal 

 axis, i.e. from above, the circular border of the body proves to be 

 crenulated, with the cilia arising from the grooves. Very likely 

 Folliculina is furnished with longitudinal myonemes, and the 

 remarkable contractility of the body seems to confirm this, although 

 I could not satisfy myself of their existence. 



The cilia, as a rule, hardly seem to deserve their name, for they 

 either do not move at all or their movements are very weak and 

 slow, and moreover they are very indistinct; one might think 



