18 PROCEEDlMiS UF THE NATION' AL MLiSEUM. vol. 53. 



they feed upon the blood of their temporary host. Upon this food 

 the various appendages develop and the sexes reach maturity. The 

 male undergoes no further change and usually remains parasitic 

 upon this first host. A few males, however, sometimes join the 

 females for the second free-swimming period, but it is highly im- 

 probable that either sex takes any plankton food during this period. 

 Their mouth parts are only suited for obtaining food parasitically. 

 The male has completed his life work, he does not increase at all in 

 size, and dies in a very short time. 



The female is seeking a final host, to which she fastens as soon as 

 it is found, and the copious supply of blood obtained from this host 

 seems to be necessary for the formation and ripening of the eggs. 

 No females of any genus produce egg strings until after this final 

 food supply has been secured. The female does not increase in size 

 during this period nor undergo any other changes, but awaits for a 

 suitable food supply. 



Hosts. — This family, like the Lernaeopodidae, is found upon fishes 

 in both salt and fresh water. In consequence of the fact that the 

 first or temporary host is always a different species from the final 

 one, the number of hosts is greatly increased. We find these para- 

 sites also upon fishes at all depths from near the surface down to 

 2,000 fathoms and over. 



Lemaeocera seems to prefer the gills of the Gadidae for a final 

 host and the gills of the Pleuronectidae for a temporary host: Ler- 

 naeolophus is found upon the gills of the parrot fish, the barracuda, 

 and the groupers of tropical seas; Peroderma often frequents the 

 lateral muscles of the sardine, the goby, and Cuvier's genus Scopelus 

 as its host; Pennella for its final host burrow^s deeply into the sword- 

 fish, the tunny, the sunfish, the dolphin, and the flying fish; Peni- 

 culus is found upon the fins of the Gadidne; Ler7iaeenwu8 penetrates 

 the flesh of the Mugilidae, the Clupeidae, the dolphin, and the bar- 

 racuda ; Lernaea chooses the gars and pike perches for its temporary 

 host, and the basses, the catfish, and the carp for its final host. 



Parasites. — The Lernaeidae are notable examples of the fact that 

 one parasite often serves as the host for another. Many of them are 

 attached to the outside of the body of the fish, where they can catch 

 ail that floats in the water, and the}^ very quickly become covered 

 with algae, ciliate infusoria, hydroids, and even barnacles (fig. 147). 

 The striped goose barnacle, Conchoderma virgatum. has been found 

 upon several species of Pennella,, and Fowler, in his Eeport on the 

 Crustacea of New Jersey (1912, p. 91), stated that many of the speci- 

 mens of Pennella filosa were parasitized with this barnacle and with 

 the hj'droid Eucope parasitica. 



Other Lemaeans from both salt and fresh water are often so 

 covered by algae that it is difficult to see any portion of the para- 



