438 D. BRYCE ON MACROTRACIIELOUS CALLIDIN^. 



gullet and between tlic rami into the oesophagus. It will be seen 

 that there they are retained until a quantity lias been collected, that 

 then takes place a constriction of the oesophagus, commencing at 

 the upper part, and that the contents are thereby forced down- 

 wards and into the stomach cavity, where they appear as a new 

 pellet, while the oesophagus begins to collect fresh materiaL As 

 soon as a pellet or two has been completed the making of more 

 coloured pellets can be stopped by changing the water, after 

 which the passage through the stomach of the coloured pellets 

 already made can easily be watched. 



It is scarcely necessary for me to add that I adhere to every 

 point of my previous references to these pellet-making forms, 

 including Call. lata. 



I have now to explain sundry terms employed in my descrip- 

 tions for the better distinction of the various divisions and parts of 

 the body of a typical Callidina, terms which, however, apply 

 equally well in most cases to the other Bdelloida. The term Body 

 is used only to denote the entire animal, and includes, therefore, 

 the three divisions — 1. Head and neck ; 2. Trunk ; and 3. Foot. 

 These in turn are composed of the so-called segments, the head 

 and neck having six ; the trunk six ; and the foot (usually) four ; 

 in all 16. 



The segments of the Head and Neck comprise the first and 

 second Rostral, the Oial, the first, second, and third Cervical. 

 The two rostral form the Rostrum (tlie anterior extremity of the 

 body when extended), whose tip is partly invertile, and bears 

 numerous tactile and motile cilia, shielded by the Rostral Lamella?, 

 two overlapping membranous plates, curiously arched. The non- 

 invertile exterior of the tip is the Rostral Sheath. The second 

 rostral is simply a broader base for the first. 



Following them is the oral segment, distinguished by the pre- 

 sence of the mouth and of the ciliated discs, conspicuous even 

 when infolded. When the mouth is opened, and the ciliated discs 

 on their pedicels are pushed forth, these, together with the ciliated 

 surfaces of the secondary wreath, are spoken of as the Corona. 

 The unciliated surface now visible, in direct dorsal view, between 

 the pedicels (and in some cases partly behind them), is the Uppor 

 Lip, which, widening as it recedes from the front, merges gradually 

 at the sides into the Collar, that wider part immediately succeed- 

 ing the bases of the pedicels. The Lower Lip is the ventral margin 



