The present paper contains the results, other than those already published, of work done in the Department of Agricultural Zoology at the Birmingham University upon the tapeworms of birds. At the commencement, a little over two years ago, the aim was to make a complete investigation of the Cestodes of British birds, both from the standpoint of anatomy and also of life-history, since, as far as I am aware, there exists no adequate description of them. It was found impossible to obtain a regular supply of any one species of tapeworm, hence the work upon one particular species could only be carried on spasmodically. The results, having to wait upon the occurrence of the material, are necessarily incomplete. Circumstances having made it necessary temporarily to postpone the work, it was considered advisable to write up and publish the results so far obtained.