21 



hungry, or pressed for food, the stickleback will sometimes swallow 

 the Arguli, but generally speaking they are avoided, and if swallowed 

 are ejected from the mouth. Their abundance is probably due to 

 their being distasteful to their enemies. Some I had in confinement 

 were readily attacked by a Notonecta, and as speedily killed. 



As to their capture, I have taken as many as a dozen on one fish, 

 and about the middle of June, when fish were plentiful, nearly every- 

 one captured had parasites attached. In captivity the Arguli, if 

 numerous, will attach themselves to the number of thirty or forty on 

 one fish, and needless to say the host lives but a short time after. 

 I once took a young roach with two parasites attached, which 

 remained so in captivity twenty-five days. T\\q Arguhis is frequently 

 captured unattached, ^Ir. S. W. Kemp having supplied me with 

 several specimens so taken. My observations as to their existence 

 in the adult state during the winter have been corroborated by a 

 capture made by JMr. Kemp in a pond at Alperton, under natural 

 conditions, as early as March 15th. Winter eggs also exist, as I have 

 previously mentioned. I am of opinion that delay in hatching and 

 development is mainly a question of temperature, as, for instance — a 

 batch of ova hatched on October 30th did not reach the third stage 

 until November 28th, and the fourth stage on December 12th. 



The average length of life of an Argulus is probably over six 

 months, and I have kept several such. They are frequently victims 

 of a filamentous fungoid disease precisely similar in its nature to that 

 •of its host. Vorticellje also infest the Argulus from its earliest stages, 

 some small captured specimens having been found almost entirely 

 covered with colonies of Vorticellas. 



A remarkable capture of three A.foliaceus \s recorded by Isaac 

 C. Thompson, F.L.S., collected by Dr. G. H. Fowler from the Faeroe 

 Channel, 1896-1897, in the "Zoological Society's Proceedings," 1898, 

 showing that the Argulus will live in salt water. These presumably 

 had been conveyed to sea by the medium of some fresh-water fish. 



I have tried various methods of staining these transparent animals, 

 with a view to a better differentiation of their structure, such as the 

 aniline dyes, picro-carmine, osmic acid, ha^matoxylin, etc. Nitrate 

 of silver, y\j per cent., is the only reagent which has given me 

 any satisfaction, and this only in staining the various ciliated organs. 

 For their preservation as permanent specimens formalin is useless, 

 .as it renders the tissues opaque. Glycerine and water, equal parts, is 

 the best means of killing them by immersion alive. For mounting 

 as microscopic objects I can recommend Farrant's medium. 



My specimens were taken from the Grand Junction Canal, 

 Paddington. 



