1906-1907.] British HydraclmidcB : The Genus Pioiia. 377 



that indefatigable collector, Mr Taverner. In England Dr C. F. 

 George has done a great deal of work, mostly on collections 

 made in Lincolnshire. Mr A. D. Michael has also done some 

 splendid work, but I do not think he has written on the genus 

 Fiona. I take this opportunity to thank the above gentlemen 

 for specimens sent, and for loans of type specimens for the 

 preparation of this paper. My own collecting has been made 

 mostly in the counties round London, in the lakes of Wales, 

 and the Broads of Norfolk. 



Life-liistory. 



Of this we know very little. The eggs are usually deposited 

 on the leaves or stem of some water-plant, anacharis being a 

 favourite for the purpose. Fiona longipalpis, Krend., generally 

 deposit their eggs in a line on the upper side of a leaf. Each 

 egg seems to be deposited separately, as the line of demarcation 

 can be plainly seen for some time. [A drawing illustrating 

 this was shown. This drawing was made direct from the 

 eggs, these being selected and drawn every second day from 

 deposition until the escape of the larvae. The eggs were 

 deposited on a leaf of anacharis on April 28, 1904, and 

 hatched on May 15, — eighteen days in incubation. It was 

 shown that the eggs enclosed in the gelatinous mass gradu- 

 ally grew until they were nearly twice the size they were 

 originally, and the line of demarcation in the horny envelope 

 had been quite obliterated.] The larvae are free-swimming, 

 but have only six legs, not eight as in the adult. These 

 larval forms no doubt now begin to look about for a host 

 to which to attach themselves, but what this host is remains 

 to be discovered. At the end of the larval stage they go into 

 an inert condition, from which they emerge free-swimmers, 

 this time with eight legs. In this stage they are called 

 nymphs. They now possess all the characteristics of the adults 

 except the distinctive sexual ones, and are, of course, very 

 small when compared with the full-grown adult. How long 

 they remain as nymphs is not known, but after passing 

 through another short inert period they become adults, and 

 rapidly develop to their full size. 



