434 MR. P. H. GOSSE ON THE STRUCTURE, FUNCTIONS, AND HOMOLOGIES 
cies*, he gives no details of the internal structure, but represents two projecting arti- 
culated setae, which he calls “ appendices de la bouche.” Of the latter, however, I 
must confess, after the examination of dozens of specimens, I can discern no trace, 
with a power of 560 diameters. 
71 . In 1850 I had discovered, in a species of Synchoeta, what seemed to me a most 
anomalous condition of the manducatory organs. As the species appeared new, I 
described it-f-, in 1851, by the name of S. mordax. The peculiarity consisted in two 
pairs of hooked jaws, exactly resembling the mandibles and maxillae of a beetle, now 
and then projected from the front, and opened with a sudden snapping motion, and 
instantly withdrawn. Each pair moved independently of the other, but in evident 
connexion with two pairs of bulbous muscles, seated deep in the breast. They could 
scarcely be discerned, when withdrawn beneath a sort of membranous lip that formed 
the frontal outline ; and no trace of them could be recognized after the animal had 
been subjected to the compressorium. 
72. Until recently, this structure completely baffled my endeavours to solve it. It 
was totally unlike anything that I was acquainted with in the whole class ; and yet 
I was quite sure of the exactitude of the observation, having witnessed the pheno- 
mena on many occasions. Very lately, however, I have succeeded, by means of the 
solution of potash, in defining the whole structure of the solid parts, and can demon- 
strate them at pleasure. I found, with surprise, that there is in them no deviation 
from the normal type, while the function and homology of the organs are greatly 
illustrated by their action. 
73 . Themastax, as before stated, is of large size, ventricose, globose, or subcubical 
in figure, with both the incus and the mallei so much bent, as to form, when viewed 
laterally (fig. 43), each two sides of a quadrangle. The f ulcrum is a slender, com- 
pressed rod, slightly arcuate. The rami are thin, elastic blades, nearly straight when 
viewed laterally (fig. 43), but arched in a forcipate manner ; the internal edges not in 
contact, but approaching at the points, which are somewhat twisted. The mallei are 
slender ; the manuhrium much bent ; the uncus a single, pointed finger, connected 
with the ramwi' by a delicate membrane, cut into teeth, — at least in S. tremula (fig. 42). 
The points of the unci form the anterior, as the points of the rami form the posterior, 
pair of snapping teeth. 
74 . The vigorous action of these jaws would lead us to expect powerful muscles, 
and we find them peculiarly thick and bulbose. The great convergent pair with 
clubbed summits, that form a conspicuous V-shaped object in the midst of the ani- 
mal, are muscles, which envelope the mallei (fig. 41), and are seen, during the mo- 
mentary protrusion of their tips, like thick gums around the bases of the teeth. A 
thick, clavate muscle also proceeds from the articulation of the uncus, and lines the 
globosity of each lateral lobe of the mastax (fig. 41). In 8. mordax a pair of muscu- 
lar bulbs are placed, one on each side of the foot of the f ulcrum : these are probably 
* Infus. pi. 21. fig. 6, A.B. t Ann. Nat. Hist., 8ept. 1851. 
