ECHINODERM LARV.E. 485 



tube-feet (t.f.). Figure 48 represents a young and still 

 pelagic Ophiuroid, probably of the same species as the 

 ophiopluteus shown in fig. 37, PL VI, found in the plank- 

 ton on April 19th, 1909. 



Larvae of Echinoidea. 



Seven species of Echinoidea are known to occur in 

 the L.M.B.C. District; and of these the larvae of five, viz., 

 Echinus esculentus, E. miliaris, Echinocyamus pusillus, 

 Spatangus purpureus and E chinocardium cor datum, are 

 known with certainty, having been reared from the egg 

 by MacBride (10), Theel (15), Krohn (9), and others. 

 Gravely and I have recognised the first three, and the 

 fifth, in the plankton of Port Erin. Of the remaining 

 three larval forms one is well known to me, but not yet 

 satisfactorily correlated with its parent species. 



Probably no member of the marine fauna of Port 

 Erin is more familiar, alike to the student of Zoology and 

 to the casual visitor, than the common sea-urchin, Echinus 

 esculentus. The ruined breakwater, the boulder-strewn 

 beach at low tide, and the depths beyond low-water mark 

 in which the dredge is used, all furnish an abundant 

 supply of specimens. In view of this fact the rarity of the 

 occurrence of its larva (figs. 49 and 50, PL VIII) in 

 plankton gatherings is remarkable. My first acquaint- 

 ance with this larva was made so long ago as June 23rd, 

 1900, when I found a few fully developed plutei in a 

 tow-netting remarkable for the variety and interest of the 

 larval forms it contained. Since that time I have again 

 and again made careful search for it, by using the tow- 

 net at the surface, in mid-water, and sunk by means of a 

 weight to within a few feet of the bottom, bill with only 

 a very small measure of success. The breeding season 

 of Echinus esculentus occurs in the early spring. In the 



