62 ANIMAL FORMS 
form great stony masses, sometimes several feet in dia- 
meter. 
64. Effects of an inactive life—In many species such a 
sedentary life has resulted in the almost complete disap- 
pearance of the lateral appendages, which therefore no 
longer serve as organs of respiration, and this function has 
been shifted accordingly on to other structures. These 
. new organs are situated principally on the exposed head, 
Bi), os 4 (Us 7 heh 
rC, 7 1s G 
oy y i. 
3 , LGN ; f “ae A 
Fig. 39.—Sedentary tube-dwelling marine worms, upper left hand Sadella (one-half 
natural size), the remainder Serpula (enlarged twice), From life. 
and Fig. 39 shows the general appearance of some com- 
mon species. The corners of the mouth have expanded 
into great plumes, sometimes wondrously colored like a 
full-blown flower, and these, bounteously supplied with 
blood-vessels, act as gills. When disturbed, the plumes are 
hastily withdrawn into the tube, and some of the so-called 
serpulids (Fig. 39, bottom of figure) close the entrance with 
a funnel-shaped stopper. While the plumes are primarily 
respiratory organs, they also act as delicate feelers, and may 
even bear a score or more of eyes; and in addition, being 
