F. M. Turnhnll — Anatomy and Habits of ]Vereis virens. 271 



The ventral cirrus of the first foot of the raale (tig, 10) is not quite 

 so long as the dorsal cirrus, but it is a little longer than the venti'al 

 cirrus of the female. In the fifth foot (fig. 11) it is a little longer and 

 much more slender than it is in the female. In the forty-fifth (fig. 12) 

 it is twice as long and of the same diameter as it is in the female. 

 In the one hundred and ninth (fig. 13) there is the same difference 

 which we see in the foi'ty-fifth. 



The difference between the ventral cirri of the male and female, in- 

 creases from anterior to ^yosterior, being greatest m the posterior seg- 

 ments. 



Beginning with the forty-fifth foot (fig. 12) a shoulder {x) appears on 

 the dorsal side of the lower ramus in the male. It increases in size and 

 definiteness farther back, but finally disappears. This shoulder 

 is never seen in the female, and is a good character for distinguishing 

 the sexes, but it requires microscopic examination. The difterence 

 between the cirri of the male and female is suflicient to distinguish 

 them without the use of a lens. 



The setae under the microscope are very delicate and beautiful (figs. 

 2. la). They consist of two parts, the shaft (a) and the blade (J). 

 The shaft has a transversely striated appearance, which is exceedingly 

 regular. The blade is held in a sort of socket in the end of the shaft, 

 and one edge is toothed like a saw. There are two forms : one in 

 which the blade is short, having its extremity blunt and slightly 

 hooked (fig. 2), and one with the blade tapering to a fine point, 

 the blade being long and slender (fig. 2a). The length varies and 

 with it the delicacy of the point. In most of the setae the latter is 

 so sharp that it seems to vanish, and can be seen only with a high 

 power. Those setse which are hooked have the hooks and toothed 

 edge turned upward; and these are always confined to the lower 

 ramus, and to the lower side of the latter in both bunches. In the 

 middle and posterior regions these hooked setae disappear, their place 

 being taken by the other kind ; but the latter are shorter than those in 

 the upper part of the bunch. The same forms of seta? are found in 

 both male and female. Those of the anterior feet are shorter than 

 those in the middle region. When viewed by transmitted light the 

 bunches present all the colors of the spectrum. 



The aciculge (figs. 12 and 22) are simple thorns, in the form of an 

 elongated cone, generally a little bent. They are black, except at the 

 base, showing through the translucent integuments of the foot. At 

 the base they are hollow and therefore lighter colored. 



