176 



Transactions. — Zoology. 



is smaller than several others, though I have several that are 

 still smaller. The introvert is of about the same length as 

 the body, though in some instances it is considerably longer. 

 In one case, mentioned below, the introvert is almost twice 

 the length of the body. This was killed slowly by adding 

 KCN to the water ; so that the total length of a fully ex- 

 tended (preserved) individual is 50mm. to 70 mm. 

 Dimensions in Millimetres. 



Type. 



Warring 

 ton. 

 (Fig.) 



Stewart Island. 



Foveaux Strait. 



(a.) 



(fc.) 



(a.) 



(b.) 



Length of body 

 Greatest diameter of 



body 

 Length of introvert . . 

 Diameter of introvert 



22 

 6 



40 

 2 



» Only 5 mm. of introvert is everted. 

 t Introvert totally retracted. 



As to the internal anatomy a few words will suffice. The 

 longitudinal muscles of the body-wall are separated into about 

 18 to 20 major and a few minor bundles. These, as in other 

 species, anastomose, so that the actual number will vary 

 according to the level of the trans-section. 



There are four retractor muscles of the introvert, of which 

 two are much stouter than the other two — from two to three 

 times stouter. All are attached to the ventral side of the 

 body- wall a little beyond the middle of the body-length, and 

 the stouter ones are attached somewhat further back than the 

 other two, almost in the same longitudinal line. 



The intestine presents 7 or 8 double coils — i.e., the de- 

 scending and ascending limbs each turn 7 or 8 times round 

 the axis of the spire. There is a spindle muscle present, which 

 is attached posteriorly as well as anteriorly. In addition a 

 slender muscle passes from the anterior end of the intestinal 

 coil, to be attached to the body-wall close to the nerve-cord. 

 A similar muscle is mentioned by Shipley as present in P. 

 varians.''- 



There are two " brown tubes " (nephridia). These are 

 comparatively long, nearly half the body-length. Each is, 

 of course, quite free, and is dilated anteriorly to form a 

 nearly spherical bladder, which opens outwards. In some 

 instances this is so greatly distended as to appear like a 

 caecum, f 



• Q.J. M. So., xxxi., p. 10. 



t An interesting variety of Physcosoma annulahnn has 3 brown tubes 

 at the same level ; but what is most misleadirg is tbe presence, at the 



