176 Transactions of the Royal Microscopical Society, 
II . — The Mastax- Framework in Melieerta ringens and Gono- 
chilus, described by F. A. Bed well; with further Notes on 
these Rotifers. 
(^Bead before the Royal Microscopical Society, June 5, 1878.) 
Plates X. and XI. 
Lord Sydney Godolphin Osborne, in January last, entrusted to me 
the agreeable duty of describing the mastax of M. ringens from a 
series of slides of that organ as dissected by him from the rotifer 
itself, and mounted. I must premise that it is quite impossible for 
me to hope to do justice to the great beauty of the contents of 
these slides, either by pen or pencil, they must be seen to be 
enjoyed ; the accompanying drawings simply express diagrammati- 
DESCRIPTIOX OF PLATES. 
Plate X. 
Fig. 1. — Details of framework of mastax of M. ringens diagrammatically 
treated, a, 6, c, form the : a, frontal \Ao,^\e 6, blade ; c, alula, dd^man- 
uhria. e e are rigid attachments, which in life are connected with the angles c c of 
each alula, and by lifting the alulee they force up the free edge 6 6 of the central 
blade of the ramus, and bring down the turreted edge of the frontal blade of the 
ramus, f is the fulcrum, the hinge, confused by flattening, see Fig. 6. pp are the 
teeth, fifteen in number, removed from their supports ; in nature they lie with 
their points fixed in the turreted serrations of the hontal blade of the ramus, their 
roots being attached to the manubria, along the lines g h. 
Fig. 2. — The letters repeated. This figure represents the free edge of the 
ramus, lifting up to tlie under side of the teeth, and bending them towards the 
rectangular position which they are seen to possess in life when masticating food. 
(Five of the teeth have been removed.) 
Fig. 3. — Explained in text. 
Fig. 4. — A mechanical illustration of the ramus, to be cut out in cardboard, 
and explained in the text. 
Fig. 5. — One of the large teeth. 
Plate XI. 
Fig. 6. — This diagram represents the hinge fulcrum and the two rami of 
Conochilus volvox. The letters refer to the same parts as in M, ringens ; the points 
c and e are united in life, as also are those parts at K and H which have been 
separated in the diagram. 
Fig. 7. — This figure is explained in the text, and represents the hinges H and 
K when the organ is at work, and shows how the arms of the ramus springing from 
K meet together, and how the arms that drive the alulcx rise upwards at H, and so 
lift up the alulee. 
Figs. 8, 9, 10, are transverse imaginary sections of the mastax, and show 
how, as the end of the alula c is lifted upwards, the points of the teeth tend to come 
downwards. 
Fig. 11 is a transverse section showing an abnormal position, explained in 
the text and seen by the writer, and arising from the manubria d, giving their 
forward blow along the teeth at a moment when the alulae c were not lifting the 
points b upwards, so that the teeth bent the wrong way at the points p. 
Fig. 12. — The eye of Conochilus. 
Fig. 13. — Corrected diagrammatic representation of wheel of Conochilus, 
showing its relation to the sinus into which the food flows on its way to the 
mastax. 
