352 ME. H. M. BEENAED ON THE 



radiate so regularly outwaixl, but have to bend about among a great network of blood- 

 lacimse wMcb are limited by connective tissue (PL XXXII. figs. 1, 5, ret). 



This irregular arrangement gradually becomes regular again. It appears to be as 

 follows, my description being based upon racquets cleared in cedar oil and studied by the 

 liighest oil-immersion lens applicable (3 mm. apochromatic of Zeiss) : — A thick epithelium 

 runs in wavy folds, as shown in the diagrammatic cross-section, fig. 8. The nerve-fibres 

 all rixn. on the posterior side of this epithelium, largely within the posterior folds 

 themselves. In the anterior folds, i. e. between the epithelium and the cuticle, the space 

 is apparently filled with blood-fluid, in which are a few blood-cells. 



Still nearer the outer edge of the fan (figs. 1 & 6) the folded epithelium flattens out 

 again, and the nerve-fibres radiate again freely outward. They terminate in a long row of 

 minute pores through the chitin of the outermost face of the bolster, but do not appear 

 to project. As above described, when the bolster rolls inward towards the furrow these 

 nerve-endings are bent down under protection of the stiff ridge. In one of my mounted 

 specimens the bolster is standing up throughout a part of its course, aj)parently unable 

 to roll round, owing to the presence of a foreign body ; on each side of this tract, 

 however, the bolster is rolled round and the nerve-endings are bent backward. 



Eig. 9 (PI. XXXII.) is the surface view of the edge of a racquet-organ of a Bhax, which 

 shows the nerve-endings bent sharply round, perhaps abnormally so, owing to the pressure 

 of the cover-glass. The protecting ridge {j)r) has also in this case been flattened out. 



I could find no trace of any muscular fibres which could effect the movements in the 

 ridges. I therefore think that the erection of the bolster-ridge is due to fluid 

 pressure. It seems also not improbable that the folded epithelium effects this erection 

 by means of the fluids contained in the folds. 



There is uo histological resemblance between tiie racquet-organs of Galeodes and the pectines of 

 Scorpio (cf. Gaubert). The "teeth" of the latter, however, in sagittal sections, look as if they were 

 erectile by means of fluid pressure. 



(5) Sensor?/ SetcB. — The Galeodidae are very richly provided with setse, of which there 

 are several specialized forms — specialized, that is, as sense-organs. I must confine 

 myself to two, having made no special study of these structures. 



1. We have the plumose bail's, which appear to be sensory, but arc not necessarily so ; 

 they are generally found grouped on the inner sides of the chelicerse, and serve, perhaps, 

 as a felt-like barrier to prevent the escape of nourisliing fluids. The elaborate sieve in 

 front of the mouth is probably due to the concrescence of plumose hairs. On the other 

 hand, the two long plumose hairs, one on each tip of the under-lip, look like sensory 

 organs. In all these plumose haii's fine staining channels can be seen running out 

 laterally from the central axis of the hair into each barb. 



2. While it is probable that all the longer hairs are to some slight extent sense-organs, 

 there are some which are highly specialized as such, notably the long fine hairs on the 

 pedipalps and on the first pair of legs, which, as above stated, is in process of becoming 

 a second pair of feelers. 



PI. XXXII. fig. 12 is a drawing of the tip of the first pair of legs (3rd appendage) of a 



