PLATE V, 



Fig. 



1. Reddish variety of Lineus gesserensis, 0. F. Muller. Enlarged under a lens. 



2. Linens sanguineus, Jens Rathke. Enlarged. 



3. Lineus lacteus, Montagu, MS. Enlarged. 



4. Enlarged view of the head of Nemertes gracilis, seen as a transparent object. 



