Structure of the Mouth in Sucking Crustacea. 255 



harmonious cooperation of all the parts of the complicated 

 machinery to one end, and, finally, to appreciate the fundamental 

 types which may be discerned in the conformation of the 

 mouth in these Crustaceans. These questions _ can be solved 

 only by a well planned, gradually progressing dissection under 

 the microscope, carried out in such wise that the natural posi- 

 tion of each part is observed with certainty— a process difficult 

 in itself, and involving the sacrifice of much time and many 

 specimens. As I shall liave no other convenient opportunity 

 in the sequel for doing so, I shall here at once briefly indicate 

 how I interpret the figures which the authors quoted have 

 inserted in their page 165 (vol. ii.) as representing the parts 

 of the mouth in Paranthura Costana, but which are not eluci- 

 dated either by references in the text or by any special expla- 

 nation. 



There are two figures marked /, of which the one to the 

 right no doubt represents one of the maxillipeds with its two- 

 jointed palpus, its stipes and cardo, together with the proster- 

 num, though the relative proportion of these parts is- not 

 accurately rendered (an observation which may be made with 

 reo-ard to several figures in this very useful work, but which 

 isliccounted for by tlie consideration that the drawings evi- 

 dently are mere sketches intended to assist the student m 

 finding the parts) . The other figure / represents, as I believe, 

 the terminal portion of the same organ. The letter e denotes 

 one of the maxilla of the first pair (our authors seem to de- 

 scribe this pair as the second) ; fig. d is no doubt a mandible. 

 The left-hand figure of the two marked with a cross I take to 

 be drawn from a preparation including portions of the first and 

 second pairs of maxillae in superposition; whilst the other 

 figure with the same mark undoubtedly represents the upper 

 lip with the clypeus, confounded by pressure into one mass*. 



* In passino- I may mention that the information given by Messrs. 

 Spence Bate and Westwood on Conilera cylindracea proves numistakably 

 that its mouth is formed for biting, and entirely agr-ees with that of 

 Cirolani, whilst differing widely from that of ^>«, which, as_ 1 have 

 shown in the former part of this treatise, is formed for suction. If, 

 therefore, we are to be guided in our systematic arrangements by the 

 structure of the mouth, and not merely by the general external resem- 

 blance (habitus), Cirolani, and with them Comlera, must not be classed 

 with J^Qa, but removed to the opposite extremity of the series of Iso- 

 poda. Having proved myself that .^c/a and Cymothoa are really sucking 

 Crustacea, I qiiite agree with our authors when they plpce Anthura next 

 to them on account of the structure of its mouth ; but this argument for 

 their classihcation seems hardly consistent with their own statement 

 (vol ii p 273), that in " the second subtribe of the parasitical normal 

 group of the Isopoda [comprisingSeiplidfe, .iSgidse, and Cymothoida] 

 the oral organs are formed for mastication." 



