12 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 8o 



LEG-SEGMENTATION AND MUSCULATURE IN THE PROTURA 



Leg segmentation in the Protura was first described by Silvestri 

 (1907), while the musculature was first studied by Berlese (1910). 

 More recently Prell (1912) made the leg segmentation and muscu- 

 lature in this order the subject of a special paper. In regard to the 

 segmentation of the movable limb there has been agreement among 

 these three workers. All recognize the large somewhat triangular 

 basal segment (pi. 4, fig. 7) as the coxa, the small ringlike second 

 segment as the trochanter, the next and largest of all the segments 

 as the femur, the two following smaller segments as the tibia and 

 tarsus respectively. Prell also calls the foot the pretarsus. In regard 

 to the musculature there are some differences in the results of these 

 workers, the chief of which has to do with the tarsus. Berlese ( 1910) 

 figures a conspicuous muscle arising from the dorsal wall of this seg- 

 ment and attaching to the dorsal aspect of the foot in Acerentomon 

 doderoi. The action of such a muscle would be to extend the claw. 

 Also in the same species both a levator and a depressor muscle of 

 the femur are represented. Prell, who worked with the same species 

 and also with Eoscntomon gcrmanicumi, finds no such extensor of 

 the claws in any of the tarsi. In all legs he found a levator of the 

 femur but no depressor. 



Prell's paper is so complete that the writer has done but little 

 beyond verifying his results except with regard to structures and 

 muscles that occur about the base of the leg. Here in front of the 

 coxa the present writer has always found two crescentic sclerites as 

 represented by Berlese (1910) for Acerentomon doderoi, but a some- 

 what different interpretation is placed on their homology and func- 

 tion. Berlese regarded the more ventral sclerite as the subcoxa or 

 trochantin and the more dorsal as the epimeron. The present writer 

 would consider the two together (pi. 4, fig. 7) as a real subcoxa which, 

 however, has largely lost its function. The shape and position of these 

 sclerites indicate that they are more of the nature of leg structures 

 than body structures. Berlese (1910) shows no articulations between 

 the more ventral one and the coxa, but Prell (1913) finds the coxa 

 articulating dorsally with the ventral sclerite near its middle and 

 anteriorly with the anterior end of the same. Although the writer 

 has always found the dorsal articulation he has failed to verify Prell's 

 results in regard to a ventral articulation. 



The musculature of the legs of Acercnttilns barheri will now be 

 described (see pi. 4, fig. 7). From the dorsal walls of the third and 

 fourth complete segments arise the fibers of the most distal muscle, 



