NORTH AMERICAN PARASITIC COPEPODS^WILSON. 



583 



The outer pair of dorsal muscle bands start also from a common 

 point of attachment in what may be called the throat of the parasite 

 on the ventral surface of the fu-st thorax segment, just behmd the 

 mouth parts. They run upward toward the doi-sal surface and rap- 

 idly outward, so that at the posterior border of the second segment 

 each is outside of the inner pair. They then run backward outside 

 of the latter and parallel with them as far as the posterior border of 

 the genital segment, where 

 they abruptly cease. 



2. Ventral muscles. — Four 

 similar bands run along the 

 ventral surface, but mth 

 these differences ; they start 

 side by side at the ante- 

 rior border of the second 

 thorax segment, diverge a 

 little, then converge, and 

 end abruptly at the poste- 

 rior margin of the genital 

 segment. Instead of the 

 median pair being fused it 

 is the two on either side of 

 the median Ime which are 

 partially fused in the fourth 

 segment and completely 

 fused in the genital seg- 

 ment (fig. 5). 



3. Muscles of the second 

 Tnaxillae. — During thecope- 

 podid stages these append- 

 ages are two -jointed and 

 furnished ^ with claws, and 

 the muscles are arranged 

 like those of other two- 

 jointed appendages. But 

 after fixation to the host and the subsequent fusion of the second 

 maxillae with the attachment filament the jomtmg in these appendages 

 is lost. And in place of the origmal musculature we now find two 

 bands of muscles running the entire length of the appendages without 

 a break, even though that be three times the length of the entire body 

 {Lernaeopodina longimana) . 



In those genera like ClaveUa, where the second maxillae are often 

 lackuig, leavmg the attachment bulla on the ventral surface of the 

 thorax, w^e still find the rudiments of a pair of longitudmal muscles, 

 which represent the original appendages. 



Fig. 5.— Ventral muscles of Achtheres ambloplitis. 



