Thompson — Fauna and Flora of Valencia Harbour, Ireland. 743 



MONSTEILLID^. 



Great interest attaches to this family through the recent im- 

 portant discovery of Professor Giard, of Paris, and confinned 

 by M. Malaquin, that the early stages of one or more species of 

 this group are spent parasitic in the body- cavity of certain 

 worms. (See Comptes Rendus, 16 novembre 1896, and 28 de- 

 cembre 1896, and 11 Janvier 1897). 



Thaumaleus claparedii was taken only once, in April, 1895. 



Thaumaleus tlionipsonii was taken twice on three occasions, viz. in 

 August and jS'ovember, 1896, and April, 1897. 



Caligid^. 

 Caligus rapax was found in the tow-net on three occasions in the 

 months of December, 1896, January, 1897, and December,. 

 1898. 



The various species of the genus Caligus, though all fish 

 parasites, are not uncommonly found as free swimmers, par- 

 ticularly at night. 



The distribution of Copepoda in deep or shallow water hardly affects 

 this collection, as it may all be classed as " Littoral Plankton," having 

 been taken either at the surface or at a depth of from one to ten 

 fathoms. There are, therefore, no specimens in the collection which 

 can be classed as specially deep-sea forms. 



In connexion with this collection, I would refer naturalists to a 

 paper by Professor Herdman, F.R.S., entitled " The Biological Eesults 

 of the Cruise of the S.Y. "Argo " round the West Coast of Ireland in 

 August, 1890 (Trans. Liverpool Biol. Soc, vol, v., p. 181). The tow- 

 net material obtained on the " Argo " cruise was placed in my hands 

 for examination by Professor Herdman, the results being given in 

 his paper. 



Both collections, but more especially that of Valencia, fiu-nish 

 evidence of the truth of the remarks made by Professor Herdman in 

 his Presidential Address to the Biological Section at the Ipswich 

 Meeting of the British Association, in 1895, as to the relatively large 

 number of genera of animals represented by the species in shallow 

 waters, and its bearing on the Darwinian principle that an animal's- 

 most potent enemies are its own close allies. In the Valencia group 

 the thirty-seven specimens recorded belong to twenty-six genera, the 

 genera being, therefore, to the species as about five to seven ; and in 

 the " Argo " gi'oup thirty-two species belong to twenty-three genera, 



