THE INTELLECTUAL OBSERVER. 



APRIL, 1864. 



EGG PARASITES AND THEIR RELATIVES. 



BY THE EEV. M. J. BEKEELEY, M.A., E.L.S. 

 (With a Tinted Plate.) 



Almost every one who is engaged in experiments on the de- 

 velopment of the ova of fishes, at the present moment quite a 

 fashionable employment, complains that they are subject to 

 the attacks of some parasite, which effectually destroys their 

 vitality. 



Various parasites indeed occasionally infest them, such as 

 green confervas, belonging to the genus (Edogonium and others; 

 but there is an especial group of organisms variously assigned to 

 Fungi and Algas, which are notoriously antagonistic to animals, 

 especially those of aquatic habits, in a low stage of vitality. 

 Elies are attacked by them while still alive, and so are our 

 aquatic mollusca, but not only these smaller beings, but fish 

 of considerable size often fall a prey to them, as is well known 

 to those who have aquaria, and as we have ourselves witnessed 

 at the London Zoological Gardens, and elsewhere. It is one 

 or more of these organisms which attack the ova of our trout, 

 salmon, and char, and therefore a few words about them at the 

 present moment can scarcely be unacceptable. 



It is now more than forty years ago since these productions 

 were tolerably well characterised, and one of their most pro- 

 minent features detected ; but it is only of later years that they 

 have been thoroughly investigated. Some of the group are 

 parasitic on confervas and other aquatic plants, but we shall 

 confine our remarks to the genera Achlya, Saprolegnia, Pythia, 

 aud Aplianomyces, so far as they affect animal substances. 



Gruithuisen appears to have been the first person who 

 observed in the clavate tips of the threads of one of them, 

 Saprolegnia fer ax (Figs. 1 — 6), a multitude of minute spore-like 

 bodies, which escaped from them and moved about when free 

 like Infusoria. This observation, on which the genus Sapro- 



vol. v. — NO. III. M 



