COMPARATIVE MORPHOLOGY OF THE GALEODlDJi:. 33& 



Special Ilusculaiure of the Limbs. — This need not be described in detail ; we may- 

 confine ourselves to certain points of special intei-est. 



The muscles moving the chelicerse on the body are entirely confined to the ceplialic 

 lobes ; the significance of this has already been pointed out [of. supra p. 309 and 

 PI. XXX. fig. 9, where the shaded portion represents this musculature). 



The muscles moving the other limbs on the body are not numerous, owing to the 

 fixation of the coxse, within which the chief muscles for moving the limbs upon the coxse 

 lie. Nevertheless, certain muscles, especially those for elevating the limbs, run from the 

 body-walls or from the endosternite and help to move the trochanter and (?) femur. 

 These cannot here be described in detail ; one muscle, however, deserves attention. 



A large muscle (PL XXX. fig. 10, ep) runs from the inner and vipper surface of the 

 endosternite on each side to raise the pedipalps. This muscle is of great length and 

 its fibres are very thick. The endosternite is an infolding between the 3rd and 4th 

 segments, whereas this elevator of the pedipalp should be attached to an infolding Ijetweea 

 the 2nd and 3rd *, as it apjjareutly is in the Spiders. This first pair of apodemes of the 

 endosteruite of the Spiders is now presumably represented in Galeodes only by a pair 

 of small fibrous plates fastened by bands to the endosternite (p. 320). The elevator of 

 the pedipalps might at one time have been attached to these plates and have shifted 

 secondarily in coui-se of time on to the second pair of apodemes, /. e. on to the endo- 

 sternite, the great expansion of which sujiplies a large surface of attachment. 



The other limb-muscles coming Ironi the endosternite run into the 3rd and ith limits, 

 as they miglit be expected to do from the nature of the endosternite as an infoldino- 

 between the 3rd and 4th segments (PI. XXX. fig. 10). 



The limb-muscles of other Arachnids cannot here be discussed ; great differences naturally prevail, 

 owing chiefly to the ditierent arrangements of the cox;e. In the Arachnids with movable cox», e. g. 

 Spiders, all the body limb-muscles are attached to tliese coxae, while the limb-muscles proper (i. e. of 

 the proximal joints) lie in the coxse. In other Arachnids again, e. g. Phri/nus, the posterior faces of 

 the movable coxa are prolonged as stout sclerites into the body and attached by muscles. But it is 

 impossible here to go into details ; the various developments of the endosternite alone would make any 

 close comparison difficult and complicated. 



The Muscles of the Alimentary Canal. — The anterior portion of the chitin-Hned 

 oesophagus is converted into a sucking-apparatus, which is expanded by a very powerful 

 array of muscles attached to the walls of the beak ; the contractions are brought about 

 by a much weaker system of circular muscles (PI. XXVIII. fig. 3). While the dilators 

 of the oesophagus are clearly transversely striated, the constrictors are but very faintly so, 

 if at all. On reaching the central ganglionic mass, the narrow oesophagus is surrounded by 

 a thin layer of circular muscles. I have failed to find any cross-striation in these muscles. 



On emerging from the central nervous mass, a pair (?) of muscles attach the oesophagus 

 to the posterior fold of the cephalic lobes ; their contraction would tend to draw it backward 

 through the nerve-mass. These muscles may counteract some of the more sloping of tl)e 

 dilator muscles of the piunping-aj)paratus, which would tend to pull the oesophagus 

 forward (PL XXVIII. fig. 5). 



* On the justifiable assumption that originally the muscles for each limb belonged to the segment which carries it. 



45* 



