EXPLANATION OF PLATE IV. 
Fig. 1. Adult worm ( Polydora ) enlarged under a lens. 
„ 2. Great hooks of the fifth segment of the body ; a , as usually seen 
in the separated and perfect organ under pressure ; b, more 
complete as obtained in the living animal or in a favourable 
spirit preparation x 700 diameters. 
„ 3. Spear-tipped bristles accompanying the former x 700 diameters. 
„ 4. Hooks of the posterior region of the body ; a, pressed between 
two glasses ; b, seen ki front, so as to exhibit both wings, x 700 
diameters. 
„ 5. Front and side view of two of the bristles of the same species, 
x 700 diameters. 
„ 6. Caudal segment and its cup, x 210 diameters. The whole of the 
figures and explanations after Prof. W. C. McIntosh. 
