PHYLUM TROCHELMINTHBS 



329 



Order 6. — Seisonida. 



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

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



cv 



Fia. 268.— Paraseison asplancbnus, female x 2S0. a. genital aperture ; hr. ganglion ; /. 

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



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

 a perforated disc. 



Systematic Position of the Examfle. 



Brachionus ruhens is one of the several species of the genus 

 Brachionus : it belongs to the family Brachio^iidm, and to the 

 sub-order Loricata of the order Plovina. 



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 Brachionida> 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 



