TAKEN AT ALNMOUTH, NOllTHUMBERLAND. 439 



nated prominence of the cephalothoracic integument; further 

 developments are seen in figs. 13 and 14, and in fig. 16 is shown 

 what is probably the final stage of the intermediate life history. 

 At the distal extremity in figs. 1 3 and 1 6 may be noticed small 

 sucking discs (?), and in fig. 16 a structure, which Prof, Gr. 0. 

 Sars has called in a similar organism, the byssus thread*'. The 

 probability seems to be that the parasite represents the larval 

 stage of a fluke of which the Acartia is the intermediate host. 

 Where the final steps of the fluke may be attained it is impos- 

 sible at present to say ; probably, I think, in the intestine or on 

 the outer surface of some fish. The dab, being very abundant 

 in the river Aln, may perhaps be the final host, but I cannot 

 hear of any fluke having as yet been found in or on it. 



Alcyonidium HiRsuTTJir. This beautiful Polyzoon seems to 

 grow abundantly on the reef of rocks immediately to the north 

 of Alnmouth. I could always find it among the heaps of washed- 

 up seaweed there, but, excepting a few very small young speci- 

 mens I did not succeed in finding it growing. Probably it lives 

 chiefly a little beyond low-water line, I mention it here on 

 account of the minute Algse which live on and in it in great 

 abundance, — so abundantly indeed that the creature itself is 

 often quite masked by its deep red investment. This at first 

 deceived me into the belief that I had got an actual red Alga. 

 I am indebted to E A. Batters, Esq., for examining and naming 

 these parasites, and for kindly allowing me to print the following 

 list of them. 



Endozoic sjjecies. 



Chantransia endozoica, Darbishire. 



Epicladia flustrse, Eke. 



var. Phillipsii, Batt. 



* The description here referred to will be found iu Prof. G. 0. Sars' report on the 

 Schizopoda of the "Challenger" expedition, p. 221, plate 38. Respecting the byssus 

 Sars says " the most peculiar feature is the mode in which the parasite is affixed within 

 the body cavity of the Schizopod. For this is not eifected by any of the sucking discs, 

 but with the aid of a kind of byssus excfeted from the posterior end of the animal and 

 dispersed within a peculiar sac-like body lying transversely within the posterior part 

 of the body cavity of the Schizopod and at least with one of its extremities firmly con- 

 nected with the otiter skin." A structure very similar to this is seen at fig. 19, Plate 

 XIII. : the byssus thread is marked b. 



