300 MK. H. H. STIRRUP ON 



fused propterygium and metapteiygiuni *. The articulation with 

 the pectoral girdle was normal, and there were 17 complete and 

 1 incomplete radials (text-fig. 60). The fin on the right side was 

 typical, the epiphyses only being united ; it had 17 radials. 



Budgett t has described and illustrated a small flange of 

 cartilage on theexternal side of the metapterygium in the larval 

 Polypterus, which suggests traces of a biserial arrangement of 

 radials on the metapterygium. He says, " On the free edge of 

 the metapterygium, at its distal end, is a slight flange of cartilage, 

 seemingly forming a rudimentary continuation round the distal 

 end of the radial cartilage." I saw no traces of this cartilaginous 

 flange, but on removing the dermal skeleton from the fins I 

 found a flange in the position described, and it was apparently a 

 continuation of the small distal cartilages. But on examining 

 sections it proved to be connective tissue without any cartilage. 



24. A Descriptive Study o£ an Oligochgete Worm o£ the 

 Family Enchytrseidge ; with an Appendix on certain 

 Commensal Protozoa. By H. H. Stirrup, B.Sc. 

 (Birm.), Lecturer in Agricultural Biology, East 

 Anglian Institute of Agriculture, Chelmsford J. 



■"Received March 10, 1913 : Read March 18, 1913.] 



(Plates XLYI.-XLIX.§ and Text-figures 61-67.) 



Index. ,, 



I'ages 



UnchytrcBus pelhicidus, Anatomy of 303-316 



Commensal Protozoa 316-317 



Summary of Observations 317-319 



Introduction. 



The object of the following paper is to give as full a description 

 as possible of a typical Enchytreeid or " white worm." In spite 

 of the descriptions of Enchytraeids given by Vejdovsky (16), 

 Michaelsen (8, 9, 10), Friend (5, 6), Southern (11, 12, 13), etc., 

 there seems to be need for such a straightforward description, 

 especially of certain points about which much vagueness and 

 difference of opinion exists. The knowledge of our British 

 Enchytrseids is increasing ■ rapidly every year, chiefly owing to 

 Southern in Ireland and Friend in England, but almost all 

 recent work in connection with Enchytrseids has been purely 

 systematic, species new to the British Isles and also new to 

 science being discovered quite frequently. 



* Festschr. fiir C. Gcgenbaur, Part I. 1896, p. 295. 

 • + Trans. Zool. Soc. London, vol. xvi. pt. vii. p. 329. 

 X Corai-nunicated bv Prof. F. W. Gamble, F.R.S., F.Z.S. 

 § For explanation of the Plates see pp, 320-321. 



