In order to convey to my readers the antennæ-like character of the camerostome in Galeodes (Fig. [101]), and its position, I give a figure (Fig. [94]) of the organ from its dorsal aspect, after removal of the cheliceræ and their muscles. A side view of the same organ is given in Fig. [95] to show the feathered termination of the camerostome, and the position of the dependent accessory portion (l.l.) (Croneberg's 'untere Anhang') with its single long antenna-like feather. In both figures the alimentary canal (al.) is seen issuing from the conjoined supra- and infra-œsophageal mass.
As is seen in the figures, the bilateral character of the rostrum, as Croneberg calls it, is apparent not only in its feathered extremity but also in its chitinous covering, the softer median dorsal part (left white in figure) being bounded by two lateral plates of hard chitin, which meet in the middle line near the extremity of the organ. In all the members of the scorpion group, as is clearly shown in Croneberg's figures, the rostrum or camerostome is built up on the same plan as in Galeodes, though the antenna-like character may not be so evident.
Fig. 95.—Lateral View of Brain and Camerostome of Galeodes.
gl. supr. œs., supra-œsophageal ganglion; gl. infr. œs., infra-œsophageal ganglion. The rest of the lettering same as in Fig. [94].
When we consider that the first pair of antennæ in the crustaceans are olfactory in function, Croneberg's observations amount to this—
In the arachnids and their allies the first pair of antennæ form a pre-oral passage or tube, olfactory in function; the small mouth, which opens directly into the pharynx, being situated at the end of this olfactory passage.
Croneberg's observations and conclusions are distinctly of very great importance in bringing the arachnids into line with the crustaceans, and it is therefore most surprising that they are absolutely ignored by Lankester and Miss Beck in their paper published in 1883, in which Latreille only is mentioned with respect to this organ, and his term "camerostome," or upper lip, is used throughout, in accordance with the terminology in Lankester's previous paper. That this organ is not only a movable lip or tongue, but essentially a sense-organ, almost certainly of smell and taste, as follows from Croneberg's conclusions, is shown by the series of sections which I have made through a number of young Thelyphonus (Fig. [102]).
Fig. 96.—Median Sagittal Section through a Young Thelyphonus.