MORPHOLOGY OF THE COPEPODA, 291 



III. On the Division of the Body, and on the Oral Organs 

 of the Parasitic Crustacea (figs. 6 — 12). 



Notwithstanding tlie valuable researches in recent times of 

 Burmeister, Rathke^ Kroyer, Van Beneden, and others, in 

 the subject of the parasitic Crustacea, we are by no means, as 

 yet, fully acquainted with the structure and morphological 

 divisions of the body in these creatures. It is only by ex- 

 plaining the significance of each division of the body, and of 

 each member in every genus and species, that we shall be 

 enabled to lay a foundation for any correct estimation of the 

 relations between the parasitic Crustacea and the free Cope- 

 pods, as well as of the mutual relations of the separate forms 

 to each other. With this object in view, I endeavoured, on 

 a former occasion [vide my work, * Ueber den Ban und die 

 Entwicklung parasitischer Crustaceen,^ Cassel, 1858), to ex- 

 plain the structure of Chondr acanthus from the morphological 

 conditions presented in the young condition, and, at the same 

 time, approached the subject of the division of the body in 

 Lernanthropus and Kroyeria. But I was unsuccessful in 

 indicating the relation of the oral organs to the corresponding 

 parts in the Copepoda ; and was also- unable, from the limited 

 amount of materials at my disposal for observation, to arrive 

 at any general considerations embracing the separate families. 

 These deficiencies have been supplied in the following obser- 

 vations. 



It is well known that Milne-Edwards and Audouin have 

 attempted to point out the existence of a definite law govern- 

 ing the number oflimbsinthe Siphonostomata — a term under 

 which, since Blainville, have been included the higher, dis- 

 tinctly annulated parasitic Crustacea'^ — starting with the idea 

 that the differences in the formation of the limbs in the 

 Crustacea arise only in modifications of similar (or homolo- 

 gous, parts. IMost Crustacea, it was said, lead a free life, and 

 feed upon solid substances, and are, therefore, provided with 

 masticatory organs ; the parasitic forms, on the contrary, 

 are nourished only on fluids, and consequently must have 

 the homologous organs transformed into a suctorial appa- 

 ratus. 



* The proof of the incorrectness of this term, which !ias been overlooked 

 by Milue-Edwards ('Hist. Nat. des Crustacees'), altliough it had been pointed 

 out by Wiegniann ('Grundriss der Zoologie,' 1S32), is derived simply from 

 the oral armature of the Lernteopoda and LennEeee, which have an equally 

 good title to be termed Siphonostomata. 



