6 BRITISH PARASITIC COPEPODA. 



those of Chondracanthiis, Lerneopoda, and Clavella. 

 The fact that males are found upon egg-bearing 

 females of these genera is due to their power of loco- 

 motion having been lost when they reached the adult 

 condition. When once they have settled down on a 

 female and matured they are unable to change their 

 position to any extent. Fertilization of the female is 

 effected early in its life, before the metamorphoses are 

 completed. The resulting embryos pass out from the 

 two oviducts and remain attached to the external 

 apertures either in single or multiserial columns, each 

 being enclosed in a sac, until they hatch. In Chondra- 

 canihus zei the columns are very much compressed and 

 resemble miniature oval biscuits. The period of incu- 

 bation extends over several weeks. The young para- 

 sites hatch out as free-swimming nauplii. These 

 undergo metamorphoses, which in some forms, after a 

 particular stage is attained, are retrogressive, finally 

 leading to the adult condition. 



The following is a short account of the anatomy of 

 two members of very different families, the Caligoida 

 and the Lernaeoida. For fuller details the Memoir 

 published by the Liverpool Marine Biology Committee 

 and the reports by C. B. Wilson on North American 

 Parasitic Copepods should be consulted. 



TRIBE CALIGOIDA. 



The species chosen to represent this tribe is Lepeo- 

 phtheirus pectoralis (Miiller). This parasite is some- 

 times very common on the fins and body of the 

 flounder or "white fluke" (Pleuronectes /Jesus). It 

 also occurs on other members of the Pleuronectidse. 

 Although Lepeophtheirus pectoralis does not confine 

 itself to any particular part of the exterior of its host, 



