1909] Anatomy and Relationship of spiders 17 



I used as material transparent legs of small spiders. They 

 can be studied in life, or after enclosure in glycerin, or by fixing 

 the whole leg in picric acid which stains intensely and perma- 

 nently yellow the muscles and by enclosing it then in Canada 

 balsam. Side views were controlled by dorsal and ventral views 

 of corresponding segments. In some cases sections were neces- 

 sary and the parafhn-method was used. Besides small spiders I 

 have also studied the muscular system in several very large spi- 

 ders, such as Heteropoda venatoria, Ctenus malvernensis sp. n., 

 Lycosa carolinensis, Pachylomerus nidulans and unidentified 

 species of Eurypelma. In all these the muscles can be isolated with 

 the aid of dissecting instruments even without a magnifying glass. 



Coxa. Enclosed in the coxa are five muscles one of which 

 really belongs to the trochanter and will be described with the 

 other muscle of that segment. The four muscles belonging to the 

 coxa are: i. M. flexor trochanteris (Fig. 3, fl. tr.) This niuscle 

 arises from the episynaxial surface of the coxa and partly from 

 the chitinous septum which occupies the synaxial plane of the 

 coxa and divides its anterior two thirds into an upper and lower 

 half. The muscle is inserted with a tendon into the proximal 

 epi-edge of the trochanter. 2. M. extensor trochanteris (Fig. 3. 

 ex. tr.), the antagonist of the preceding arises from the hypo- 

 synaxial surface of the Coxa and partly from the septum. Its 

 tendon is inserted into the proximal hypo-edge of the trochanter. 

 3. M. promotor trochanteris, a broad muscle with parallel fibres 

 which arise from the prosymmetrical surface of the Coxa and are 

 inserted without tendons into the proximal prosymmetrical edge 

 of the trochanter. 4. M. retractor trochanteris (Fig. 3. r. tr.) the 

 antagonist of the promotor occupying the symmetrical position 

 on the retro-side. 



Trochanter. Two muscles are enclosed in the trochanter. 

 I. M. flexor femoris longiis (Fig. 3. fl. f. 1.) a weak muscle which 

 arises from the coxal septum and is inserted by means of a tendon 

 into the proximal epi-edge of the femur. Gaubert, who calls this 

 muscle "abaisseur," describes it as arising from the inferior 

 (Hyposynaxial of my terminology) surface of the coxa, not from 

 its septum. I think that in some cases I have seen fibres running 

 in that direction, but I am not positive about it. The function 

 of this muscle is certainly not that of the common flexor but it is 

 not an "abaisseur" (depressor), since it probably helps the flexor 

 bilobatus to lift the femur and at the same time tends to bring 



