feDELLOID ROTIFERA OF SOUTH AFRICA. 6l 



This is the species of Philodina referred to by Murray (10), who 

 gave some figures of it. The colour is sometimes light lemon, 

 but usually is bright yellow in the trunk. The ovary frequently 

 shows a red tinge. It is a very large and powerful animal, one of 

 the largest of the moss-dwelling species ; and though not very 

 much longer than P. fraelonga, is much more massive. It quite 

 rivals M. russeola, but is not quite so heavy in the rump and foot. 

 It creeps very steadily with long strides, planting the toes well up 

 under the head, and without any jerky action. When feeding, it 

 keeps on ceaselessly swaying the head round about, and up and 

 down, in a very lazy sort of way, so that the focus is being con- 

 tinually slowly altered. 



The corona is of very great size — up to 1/1 35th inch in the largest 

 examples — it is larger, and even more striking and handsome than 

 that of P. fraelonga, with equally circular discs. On account of 

 its wheels being so round and wide, and the ciliated rims stand- 

 ing out so clear of the pedicels, there is presented the most perfect 

 illusion, in any rotifer, of two cog wheels in motion. There seem 

 to be about fifteen cogs or triangular bunches of cilia on each 

 wheel. Some friends, on being shown the wheels, could hardly 

 be persuaded that there was no rotation. The corona, collar 

 and neck are to each other in the proportions 45, 30 and 20. 



On each wheel is a stout peg bearing a bunch of, at least, three 

 long Setae. On the ventral side of the sulcus, just between the 

 pedicels, there is a ridge or membrane with a deep gap, which 

 evidently exercises a selective action on the particles streaming 

 past. The sulcus is nearly as wide as the disc, but the discs lie 

 so close on to the sulcus that the great cilia play in and round it 

 in such a way as to interfere almost completely with a view of 

 the borders of the upper lip, and to make the sulcus look narrower 

 than it really is. 



The pedicels move independently of each other ; one wheel may 

 be seen being twisted round or bent over, while the other re- 

 tains its position. Both wheels may be turned over in the one 

 direction, till they appear to revolve in parallel planes. Some- 

 times they are pushed towards each other till the straight front 

 margin of the upper lip becomes a deep serrated V. A very 

 common position is with the extreme ends of the corona bent, 

 symmetrically, well down. 



At the first glance the upper lip seems a very simple one, but to 



