48 



females sectioned in various directions, the conchision has 

 been arrived at that the spermatozoa at once pass up the 

 rudimentaiy oviduct to the ovary and fertilise the eg^gs. 

 This probably accounts for the difference between the 

 ovary of an adult Lernwa and Lepeophtheiriis. No trace 

 of a receptaculum seminis could be made out in the adult. 



Life History. 



The development of the embryo has not been worked 

 out by the present author. An excellent Avork by D. 

 Pedaschenko* contains a full description and figures of 

 the developing embryo. 



The young Lerna'a hatches out as a nauplius, with 

 three pairs of appendages, representing the rudimentary 

 antennules, antennae, and mandibles (Plate lY., fig. 2, 

 nat. size, •45 mm.). It then after a short pelagic life, 

 settles on the apex of the gill filaments of the flounder, 

 to which it adheres by a broad chitinous filament, and 

 passes into a cyclopoid form (Plate lY., fig. 4). The 

 young Lernaia are occasionally found on the gills of the 

 plaice and lumpsucker. The parasite, by its attachment 

 to the gill filament, j^yroduces a marked change in that 

 organ. The whole of the apex assumes a tumid character, 

 and the filamentous plates on both sides for some little 

 distance disappear (Plate lY., figs. 8 and 9). While 

 attached to the gills the various appendages develop. The 

 male here reaches maturity (Plate lY., fig. 5), and under- 

 goes no further change. In the female a considerable 

 lengthening of the genital segment accompanies the 

 appearance of the various appendages. Fertilisation next 

 takes place ; then the young female severs its connection 



* Development of the embryo and metamorphoses of Lerncea branchia- 

 lis. Trav. Soc. Imp. des Naturalistes de St. Petersbourg, vol. xxvi., 

 livr. 4, No. 7, Sect, de Zool. et de Physiologie, 1898. (In Russian, with 

 German resume). 



