308 ORESSWELL SHEARER. 



belonging to an entirely different set of organs from those of 

 the nephridia, viz, the coolomoducts of Lankester's nomen- 

 clature. 



5. Muscular System, 



The muscular system has been described by Foettinger, 

 whose account is correct in its main particulars. The muscles 

 of the ti'unk region, as described by him, consist of two 

 groups, the dorsal and ventral longitudinal, and the irregular 

 oblique or transverse muscles. It is to these last that I wish 

 to call particular attention in the present account, as they 

 are only mentioned briefly by Foettinger. 



In addition to this I have been able to add new details in 

 the division and arrangement of the fibres of the longitudinal 

 muscles that escaped Foettinger's observation. 



A. Longitudinal Muscles. 



The chief muscles of the body are these powerful longi- 

 tudinal bands. They have already been described by 

 Foettinger in considerable detail. They consist of two 

 dorsal and two ventral sets. Each band is composed of from 

 twenty to thirty fibres, flattened dorso-ventrally. They are 

 attached by their outer margins to the cuticle, while their 

 free edges project into the body-cavity. In the generative 

 segment their number seems reduced, but this is due to their 

 confinement Avithin a limited space — against the gut dorsally 

 and the nerve-cord ventrally. In the caudal region they 

 spread out, forming a more or less complete wall round the 

 segment, only interrupted dorsally by the gut and ventrally 

 by the nerve-cord. They split up in the head and tail regions, 

 sending fibres to the jaws and the anterior and posterior feet. 

 In the head dorsally they converge on one another, uniting 

 in the median plane, and are inserted in the anterior surface 

 of the jaw apparatus. The ventral bands, on the other hand, 

 divide into two sets of fibres, the outer of which split again 

 to supply fibres to the anterior and posterior surfaces of the 



