INTERNAL AXATOMY OF BDELLA. 521 



3. A fasciculus arising from the dorsum a little in fi-ont of the auterior eye, rather 

 more toward the side of the l)ody than numbers 1 and 2, and inserted in the ventral 

 thickened sclei'ite or ridge at the jiosterior edge of tlie aeetal)ulum of the first leg. 



4. A fasciculus arising from tlie dorsum a little beliind the posterior eye, and inserted 

 in a similar manner to No. 3 at the posterior edge of the acetabulum of the second leg. 



5. A fasciculus close to the side of the body arising from the dorsum a little behind 

 the vertical plane of the coxa of the second leg; passing diagonally backward and down- 

 ward and inserted in the ventral surface a little before the third leg. 



6. A fasciculus arising from the dorsum just anterior to the genital organs, i. e., just 

 anterior to the great mucous glands of the male, passing almost perpendicularly down- 

 ward and inserted in the ventral cuticle. 



7. A fasciculus arising from the dorsum a little anterior to the embedding-sac in 

 £. Basteri, and in a corresponding position in the body of such species as have not 

 any embedding-sac, and inserted in the posterior edge of the acetabulum of the 

 foiu'th leg. 



8. A fasciculus near the side of the body arising from the dorsum about the middle of 

 the embedding-sac, but outside that organ, and inserted in the ventral cuticle some little 

 distance posterior to the fourth leg. 



There is also a fasciculus of rather fine muscles arising from the dorsum and inserted 

 in the anterior part of the endosternite, and another of stronger muscles arising from the 

 dorsum and inserted near the posterior termination of the endosternite. 



The Muscles of the Mai/ d ib I es.— The muscles which move the small terminal joint of 

 the mandible, i. e. the movable joint of the chela, are shortish ; they are wholly contained 

 in the bulbous proximal part of the mandible, and are inserted into the terminal joint by 

 means of very long tendons passing the whole length of the narrow distal part of the 

 mandible. The retractor muscles, which serve to open the chela, are few and arise from 

 the roof of the mandible; the extensors, which close the chela, are more numerous and 

 more powerful ; they arise from the lower a,nd outer sides of the mandible. The teudou.s 

 from each set of muscles unite with their fellows of the same set, and form a single tendon 

 which is inserted as stated above. 



The levator muscles of the whole mandible appear to be a group of short, thick, 

 diagonal muscles arising from and just behind the lower posterior edge of the mandible 

 and inserted into its i;pper posterior edge, which bends shari^ly but diagonally upward, 

 and extends further backward than the lower edge. There are also some muscles 

 apj)arently serving to give a slight lateral movement. 



The muscles of the legs do not differ sufficiently from what has previously been 

 described by various authors relative to more or less closely allied creatures to make it 

 worth while to describe them at any length. As before stated, the principal muscles 

 which move the whole leg arise from the endosternite ; but some few serving to give a 

 somewhat revolving motion arise from the epimera, which are very slight structures, in 

 fact little more than thickened margins to the acetabula of the legs, and from the 

 neighbouring cuticle : all are inserted in the proximal end of the coxa. The muscles 

 which move the individual joints of the legs usually arise just in front of tlie posterior 



