210 F. M. Tumhidl — Anatomy and Habits of Nereis virens. 



distinctly in some of my figures of the feet of the male. The superior 

 ligula is of about the same size and shape as the inferior ligula. The 

 lower ramus is a little more developed than it is in either the first or 

 second feet, but the inferior cirrus (A) is shorter. 



The fourth foot (fig. 6) is more highly developed than the third ; 

 but the inferior cirrus is shorter in comparison with the lower ramus. 



The fifth foot (fig. 7) is still more highly developed than the fourth, 

 and the superior ligula is larger than it is in the preceding feet. The 

 dorsal and ventral cirri are both smaller. If we now compare the fig- 

 ure of the fifth with the figures of the first and second feet, the differ- 

 ence is seen to be considerable, particularly in the length of the cirri. 



The superior ligula {b) begins to increase in size at the fifth foot, 

 and continues to do so, until in the forty fifth (fig. 8, h) it is 

 larger than any other part of the foot. It has also become flat 

 and pointed. The shoulder (?") is much larger. The inferior ligula 

 [d) is also flat and pointed. A posterior setigerous lobe {k) is now 

 large enough to be easily seen. The posterior setigerous lobe (/) of 

 the lower ramus is somewhat pointed, and its lower edge is oblique. 

 The anterior setigerous lobe (e) is now as long as the posterior seti- 

 gerous lobe, and its two divisions are nearly equally developed. The 

 inferior ligula {g) is rounded and somewhat tapering toward its 

 extremity. The dorsal and venti'al cirri are now quite small, particu- 

 larly the latter, while otherwise the foot is much larger. The setse 

 have become longer and more perfect, from the anterior toward the 

 posterior, attaining their maximum in the middle region of the body. 

 The aciculiB are also larger here than in either the anterior or pos- 

 terior regions ; although, in the posterior region they are longer in 

 comparison with the size of the foot than anywhere else. 



The one hundred and ninth foot (fig. 9), as shown by the figures, is 

 nearly the same in form as the forty-fifth, but smaller. 



On comparing the first, fifth, forty-fifth and hundred and ninth 

 feet of the female with the same in the male, we find that there is a 

 marked difference in the cirri. The dorsal cirrus in the first foot of 

 the male (fig. 10) is one-half longer than it is in the female, and it is 

 larger in proportion. In the fifth foot (fig. 1 1 ) the difference is the 

 same. In the forty-fifth (fig. 12) the dorsal cirrus of the male is longer 

 and also slenderer than it is in the female. In the one hundred and 

 ninth foot (fig. 13) the dorsal cirri are about the same in length, but 

 those of the male are more slender. 



The difference between the dorsal cim decreases toward the posterior 

 end of the bodi/, being greatest in the anterior segments. 



