SEA-FISHERIES LABORATORY. 107 



versa, an axial decussation being formed. The dorsal 

 sheaths themselves are not connected together by muscle 

 fibres, nor are the ventral ones. (3) Radial fibres inserted 

 into a peripheral fibrous zone beneath the integument. 

 Some of these originate on the outer parts of the proboscis 

 sheaths, while others seem to take origin in the dense 

 parenchymal tissue in the axial part of the scolex. These 

 bundles are represented as transverse in Text-fig. 1, 

 but they are really oblique (see fig. 5, PI. I). They 

 are relatively strong and are very numerous. Not all the 

 fibres originating on the outer parts of the proboscis 

 sheaths belong to this series, for some of those starting 

 from the dorsal sheaths run towards the ventral parts of 

 the scolex, and vice versa, a decussation being formed on 

 either side. Others taking origin on the dorsal and 

 ventral parts of the sheaths run into the tissues of the 

 bothridial suckers. (4) Transverse fibres running across 

 from side to side of the scolex, and passing between the 

 proboscis sheaths. (5) Fibres passing outside the sheaths 

 in the lateral parts of the scolex ; these run dorso- 

 ventrally. There are relatively few fibres in series (4) 

 and (5). 



Series (1) and (2) are situated anteriorly to the 

 central nervous system. Behind the latter the only 

 muscle fibres are those connecting together the bothridia. 

 These (Text-fig. 2) run external to the proboscis sheaths. 



Longitudinal muscles. These originate as two series 

 of fibres proceeding from the outer surfaces of the 

 proboscis bulbs. They become gathered up into two 

 sheets which (fig. 7, PL I) run backwards through the 

 appendix, dorsal and ventral to the main lateral excretory 

 c;mals. This arrangement is similar to that in other 

 Tetrarhynchids. 



The Central Nervous System, Ihie is represented in 



