PHYLUM TROCHELMINTHES 329 



ORDER 6. SEISONIDA. 



Marine parasitic Rotifers (Fig. 268), with the trochal disc 

 reduced, the body long, narrow, and ringed, with a long slender 



ce 



br 



ci/ 



FIG. 263. Paraseison asplanchnus, female x 230. a. genital aperture ; br. ganglion ; /. 

 foot-glands ; m. mouth ; ma. mastax ; of. oesophagus ; ov. ovary ; st. stomach. (After Plate.) 



neck-region, and an elongated foot provided at its extremity with 

 a perforated disc. 



Systematic Position of the Example. 



Brachionus rubens is one of the several species of the genus 

 Brachionus : it belongs to the family Brachionidce, and to the 

 sub-order Lwicata of the order Plaima. 



It is placed in the order Ploima in virtue of its active swimming 

 habits and the absence of looping or skipping movements. The 

 presence of a distinct lorica places it in the sub-order Loricata. 

 The family Brachionidae is distinguished by having a box-like 

 lorica open at both ends, and a long, flexible, retractile tail with 

 wrinkled surface and forceps-like termination. In the genus 

 Brachionus the lorica is not marked with ridges, and the tail is 



