279 



VIII. — Notes on a Peculiar Habitat of a Chlorophyte, 



Mycconema tenue. 



By A. D. Hardy, F.L.S., F.E.M.S. 



(Read March 20, 1907.) 



That several species of unicellular algae, commonly attached 

 to filamentous forms, and to Nitella, 'Chara, etc., are also to be 

 found leading an epizoic existence, is, I think, well known. Tlie 

 hosts in such cases are mostly Entomostraca, e.g., Simocephalus 

 elizabethce, Daphnia carinata, Cyclops quadricornis, or aquatic larvae 

 of Coleoptera, etc., the algfe attached to these being species of 

 Characium or Characiopsis which often share space with species of 

 Vorticella or Epistylis. 



The present notes refer to other algae and an unusual host 

 which came under my notice in November, 1906, through the 

 death of some "gold-fish" or carp {Characius auratus). The 

 circular pond in which the fish were kept is constructed of brick, 

 with cemented surfaces, and has a diameter of about 3 metres and 

 a depth of about 1 • 5 metre, containing, in addition to quartz- 

 pebbles and rocks, several flower-pots and wooden boxes in which 

 water-lilies are rooted. The water was kept fresh by means of a 

 pipe from the metropolitan supply of good drinking water, in the 

 form of a fountain-spray, the water escaping from below the raised 

 surface. To the rocks and flower-pots, and to the leaves and leaf- 

 stalks of the macrophytes, much algal growth adhered, the whole 

 pond having a neglected appearance, though it had been thoroughly 

 cleansed a few weeks previously. 



Twelve or more carp swam about, apparently in good health, 

 but two or three others were sluggish in movement, and when 

 caught were found to be diseased. On the backs of these, extending 

 in patches from near the eyes to about the posterior end of the 

 dorsal fin, grew flocculent impedimenta which had interfered with 

 swimming, retarding the movement of the fish much as barnacles 

 and other marine attachments impede a ship's progress. Owing to 

 etiolation the algal nature of the growth was not suspected, but 

 became evident on inspection of the third fish caught, which bore 

 a luxuriant growth, parts of which, covering patches of several square 



