riifyoiDs. 



145 



true muscles, they seem to have some power of contracting around i-csisting objects 

 which they touch. The cirri become smaller and closer together near the head, for 

 each cirrus-bearing joint develops immedi- 

 ately below the calyx, and the joints which 

 separate the cirrus-bearing joints from each 

 other develop afterwards. 



In I^. asteria the arms divide a second 

 time about si.K arm-joints above the first 

 bifurcation, and again bifurcate seven or 

 eight joints farther, the bifurcations repeat- 

 ing themselves somewhat irregularly until 

 each of the primary arms has divided into 

 twenty or thirty branches, making more than 

 a hundred arms in all. 



/*. vi/vine-thomsom\ found u[ion the 

 coast of Portugal, has the cirri separated 

 by thirty to thirty-five joints. The num- 

 ber of arms is not constant, because in 

 some cases the third radials bear one or 

 two simple arms, while in others there is 

 a third bifurcation. 



Some examples of P. muHen', and all of 

 J'. tm/viUe-thomsoni, that were dredged by 

 -\lr. Jeffreys, showed by the smooth and 

 roimded terminal joint of the stem, by the 

 shortness of the lower cirri, and by the 

 small number of joints in the lower inter- 

 nodes between the cirri, that they must 

 iiave for a long time been free, and Sir 

 Wyville Thomson states his belief that 

 the latter .species lives loosely rooted in 

 tlie soft mud, and can change its place at 

 )>leasure by swimming with its jiinnated 

 arms. 



P. tnadearkaius, dredged near the coast 

 of Brazil, has a peculiar style of arm-divi- 

 sion. Each of the ten primary arms stand- 

 ing upon the radial auxiliaries, gives off 

 two secondary arms close to its base, so 

 that there would be in all thirty arms, were 

 the arrangement absolutely ' regul.ar. The 

 arms are very robust, and the joints have 

 a tendency to widen in the middle of the 

 arm. Each arm has about seventy joints. 

 The cirrus-bearing joints of the stem are >rio.v^.- F,ntac,.nu,a,,ena. 



very short, and much inflated with round, bead-like knobs, and there are only two 

 very thin plates between the nodes. Sir W. Thomson believes that this form floats 

 about unattached. 



VOL. I. — 10 



