58 



ENTOZOA. 



separated by dissection; secondly, a double layer of perfectly 

 smooth, and continuous fibres which, cross one another obliquely so 

 as to form a double system of spirally rolled bands, encircling the 

 body from end to end ; and thirdly, a dense internal cartUaginoid 

 stratum, consisting of from fifteen to thirty extremely fine laminge. 

 According to Mr. Bastian (who has minutely examined the integu- 

 ment of Dracunculus) the spiral appearances are of a spurious 

 character, being due to a certain play of the transmitted light 

 when the structures are viewed under the microscope ; and I have 

 myself seen similar double spiral diffraction bands when examining 

 the little cysts of Trichina spiralis. Dujardin, however, further 

 states that in the region of the head — ^which in M. nigrescens 

 supports five or six papillEe — these fibres wind themselves round the 

 papillEe in a regular manner, but near to the caudal extremity they 

 form a number of irregular gyrations. Below, or in connection with 

 these papillse, " the integument presents a lacuna or conical cavity 

 in communication with the great space surrounding the oeso- 

 phagus," and Dujardin thus conceives that these openings are for 

 the passage of water into the space in question. This peri- 

 oesophageal space is said to be distinct fii-om the general visceral 

 cavity of the body, being continued, according to Dujardin, into 

 the two longitudinal cordons sarcodiques, which pass fi:'om head to 

 tail distributing to either side during their course numerous 

 transverse branches at tolerably regular intervals. Some of the 

 branches bifurcate into secondary twigs. Besides these cordons 

 sarcodiques, it is added, that if the integument be viewed fi'om 

 within, we observe two longitudinal undulating lines or ridges — 

 cretes ou cordons saillans — destined to establish a communication 

 with the muscular layer or tube charnu. These appearances evi- 

 dently correspond with the very similar structures to be seen in 

 most of the nematodes, and therefore, in the opinion of the writer 

 of this work, these structures severally represent rudimentary con- 

 ditions of the nervous and water-vascular systems. Dujardin, 

 however, expresses himself at variance with this view, as will 



