Protozoa from Fishes. 391 



of tlie same parasite. It seems almost inconceivable that 

 there is a different invertebrate host to each genus of fish, 

 and hence it is inconceivable that each geuus should be 

 infected with its own particular type of parasite. Variations 

 may be due to the age of the organism, or, what is much 

 more probable, to the different environment in which the 

 organism lives. Until more is known about the life-histories 

 of these forms, it seems superfluous to keep on creating new 

 species, and thus adding to tiie confusion already existing. 



The present work was carried on in the Dove JMarine 

 Laboratory, Cullercoats, and I wish to thank Professor Meek 

 and the staff of the laboratory for tiieir kindly help and 

 advice. 



I also wish to thank my sister and Mr. P. Gibson for 

 executing the diagrams illustrating this paper. 



Sept. 1915. 



Bibliography. 



Beneden, Yan. ' Recherclies sur les Bdellodes ou IlirudiuiSes ' (Brux- 



elles), 1663, p. 37. 

 Bentham, T. (1914.) " Some Observations ou a Leucocytozoou of the 



Siskin ( t'arduelis spuius)." Proc. Univ. Buiham Pliil. Sue. v. 



p. 139. 

 . "JNote on a Hasmogregarine of Haia batis." Report North- 

 umberland Sea-lisberies Committee, 1914-15. 

 Bul'MPT et Lebailly. " Bescription de quelques nouvelles especes de 



Trypauoiomes et d'llemogregariues de Teleosteeus luarius." 



Compt.-rend. Acad. d. Sc. Paris, 1904, tome cxxxix. p. 61.j. 

 Johnstone, J. " Internal Parasites and Diseased Conditions of Tishes."' 



Itep. 1904 Lanes. Sea-Fisberies Lab. Univ. Liverp. p. 107. Ibid. 



1905, p. 152. Ibid. 190(5, p. 192. 

 MiNCHiN, E. A. ' An Introduction to tbe Study of the Protozoa,' 



pp. 371-378. 

 MiKCHiN, E. A., & Woodcock, H. M. (1910.) "Blood-Parasites of 



Eishes occurring at Kovigno." Q. J. M. S. Iv. p. 113. 

 PoKTEU, A. (1908.) " Leucocytozoou musculi.'' P. Z. S. 1908, p. 703. 

 ivoBERTbON, M. (1910.) " Lire-cycle of Hcemoyreyarinu nicorice." 



Q.J. M. S. Iv. p. 741. 

 Saville-Xent, \V. * a Manual of tbe Infusoria,' vol. ii. p. 273. 



EXPLANATION OF THE PLATES. 

 Plate XVI. 



JVy. 1. Hamoyrer/arina cotti. i = curved form in blood-corpuscles of 

 L'ottus. 2 a & ^6 = macrogametocytes from gut of Ca/lio- 

 bdtlla. 5a = form from spleen of L'ottus. 5i=microgameto- 

 cyte. 4 = Jiii^^'i'0D^™'-'tt>C}te with discbarge of karyosomes. 

 5 a & 5 <!/ = stages in scbizogony. 



Fie/. 2. Bursal blood-vessel of Ichthijubdella anarrldchce^ tbowing spores 



