AQUATIC WORMS 77 



say the rotifer fastens its foot, stretches to its full length, 

 and after attaching itself by the head, liberates the foot. But 

 both these are slow movements, and seem to be contrary to 

 the liking of the rotifer, for usually, after walking a few 

 seconds, it opens its disc, and by means of the cilia swims 

 rapidly away. 



(Bdelloida) Rotifer vulgaris, J^th of an inch long, is a member 

 of this family. It is of special interest, not only because it 

 has given the name to the Phyllum, but also as it is peculiarly 

 able to resist drying by secreting a gelatinous covering, which 

 becomes durable when exposed to the atmosphere. 



Some of the Rotifera are roamers, and seem never happy 

 unless on the move ; others, however, are only too willing to 

 remain in one spot for at least part of their time. 



The Ploima, but for a few parasitic members, are nearly all 

 free swimmers. They seem so characteristically happy, so 

 very interested in their work, as they dash here and there, 

 dodging obstructions, occasionally resting, but only for a brief 

 moment, before hurrying off again. The Ploima are divided 

 into two sub-orders, comprising those enclosed in a case and 

 those without : 



(a) Without lorica Illoricata. 

 (6) With lorica Loricata. 



Amongst the Illoricata we find the Synchaeta a family 

 notable for the beauty of its members, all characteristically 

 active. Branchionus (sub-order Loricata) is familiarly known 

 as the Pitcher Animalcule. The lorica (case) resembles a box 

 open at both ends. The foot, which is projected out of the 

 lorica, can be drawn inside, and is a surprisingly elastic and 

 flexible structure, being able to bend in a most extraordinary 

 manner. In fact sometimes Branchionus will fasten itself by 

 its foot and whirl round at right angles, revolving at a 

 tremendous pace. Then off it will go until it settles on some 

 chosen spot and repeats the extraordinary behaviour. 



The Schirtopoda are queer little creatures, very different to 

 the ordinary type of rotifer ; in fact they resemble young 

 crustaceans to such an extent that they have often been re- 

 turned to the aquarium as members of this Phyllum. 



Padalion Mirum, one of the Schirtopoda, is about ^th of 

 an inch long. The body is drawn into long, peculiar " limbs," 

 which terminate in fanlike adornments. The head is fur- 

 nished with two eyes. The rotifer, when viewed in a certain 

 position, resembles to some extent the head and shoulders of 

 a diminutive old man, with a prominent bulbous nose. 



