AMERICAN PARASITIC ARG VLIDJE^ WILSON. 741 



soft and thev do not penetrate or even irritate the skin of the host. 

 Consequently there can be no flow of blood following their use, and 

 some other means for obtaining it must be provided. 



This takes the form of a long, pointed sting or piercing organ, which 

 is evertible and situated just in front of the mouth. This being thrust 

 through the skin into the flesh of the host quickly brings a copious 

 flow o'f l)lood, which the copepod then sucks up with its proboscis- 

 like mouth parts. 



This stage of modiflcation is exemplified in the genus Arr/ulus, and 

 is the limit at the present time. 



The genus Arguhi.s, therefore, which includes three-fourths of all 

 the species in the family, so far from being typical, is really the one 

 which has undergone the greatest modiflcation from the original primi- 

 tive type. The genus Dolop.s. especially those species which are called 

 "unarmed" by Bouvier, has undergone the least modiflcation and 

 retains most fully its primitive characteristics. 



The genus ClionopeUls is intermediate between the other two and 

 assists us in interpreting intelligently the various steps in modiflcation 

 which have been brought about by parasitic habits. 



EXPLANATION OF THP: PLATES. 



All the drawings f^.r Ijoth the text-ligures and the plates were made with a camera 

 lucida, unless otherwise stated. 



Plate VIII. Newly hatched female larva of argxilm megalops. a m, anterior maxilli- 

 ped; hr, brain; ai, endopod of first swimming foot; gl, skin glands; j) m, 

 posterior maxilliped; s b, side branch of the stomach; .s g, shell gland; 

 s r, semen receptacle; t h, tactile hairs. 



IX. Figs. 1-4, Argulus latus, ventral and dorsal surfaces, jiosterior maxilliped 

 and antennpe, all of female. 

 X. Avgnlmlatkaudn, fig. 5, ventral surface of male; fig. 6, dorsal .surface of 

 male; fig. 7, posterior legs and abdomen of female; figs. 8 and 9, 

 antennae and posterior maxilliped of male. 



XL Argulas megalops, fig. 10, ventral surface of female; fig. 11, posterior 

 maxiUiped of male; fig. 12, antenme of female; fig. 13, posterior legs 

 of male showing accessory sexual organs. (See fig. VI (in the text) 

 for dorsal surface of female. ) 



XII. Argulus alosie, figs. 14, 15, 16, and 18, ventral and dorsal surfaces, anten- 

 nae, and posterior maxilliped of female; fig. 17, posterior legs and 

 abdomen of male. 



XIII. Argulus adostomi, figs. 19-22, ventral and .h.rsal surfaces, antenuiP, and 



posterior maxilliped of female. 



XIV. Argulus fundnli, fig. 23, ventral surface of female; figs. 24 and 25, dorsal 



and ventral surfaces of male; figs. 26 and 27, antennae and posterior 

 maxilliped of male. 

 XV. Argulus pvgettensis, figs. 28-31, ventral and dorsal surfaces, antenn;e, and 



posterior maxilliped of female. 

 XVI. Argulus lepidostei, figs. 32, 34, and 35, ventral surface, antennae, and pos- 

 terior maxilliped of female; figs. 33 and 36, dorsal surface and poste- 

 rior legs and abdomen of male. 



