Gli 



the mouth-parts in the Harpacticoida, the only two thus far published. 

 The most recent works on the Crustacea, that in the Cambridge Natural 

 History by Geoffrey Smith, and that in Lankester's Treatise on 

 Zoology by W. T. Caiman, both bearing the date of 1909, adopt 

 Griesbrecht's classification. Smith says "Although much detail 

 remains to be worked out and the position of some families is doubtful, 

 Giesbrecht's scheme is the most satisfactory that has hitherto been 

 suggested.'' (p. 57.) 



Caiman, after noting that Giesbrecht makes no attempt to 

 define the position of many of the parasitic forms , says "The system is 

 therefore incomplete and can only be adopted as a temporary expedient 

 pending further investigation." (p. 101.) 



It requires about as thorough a knowledge of the Copepods to select 

 intelligently from these various schemes, backed as they are by competent 

 authority, as it would to construct an original scheme. Indeed most 

 authors have apparently found the latter the easier, since each has 

 propounded a scheme of his own. In the face of such perplexity and 

 disagreement we may well ask a few pertinent questions. 



I. Are there objections which, when impartially considered, are of 

 sufficient weight to warrant the elimination of any of these schemes ? 



a. The methods of classification used by the early writers, according 

 to which the Copepods were placed now among the insects, and again 

 with the mollusks or worms, are of course not to be thought of at the 

 present day, however useful they may have been as stepping-stones of 

 progress. This objection removes all the schemes proposed prior to the 

 time of Milne-Edwards (1840). 



b. It seems perfectly obvious that any truly scientific classification 

 must include all the Copepods, free-swimmers, semi-parasites and para- 

 sites. The transitions in body-form, in the structure of the appendages, in 

 habits and mode of life, and in the method of reproduction are so gradual 

 that no classification can claim to be complete which does not include 

 thewhole group. Milne -Ed ward s entirely separated the free-swimmers 

 from the parasites, placing them even in different subclasses of the great 

 class Crustacea. Brady's fine monograph (1878 — 80) included only the 

 free and semi-parasitic species, and made no provision for the true para- 

 sites. And Giesbrecht really included only the pelagic species which he 

 had examined. These three systems, therefore, must be regarded as 

 partial and incomplete. 



c. Finally to confine the basis of division to the female sex is as 

 pernicious here as it would be among the birds J for many of the most 

 striking characteristics are to be found only in the males. This is parti- 

 cularly true of the parasitic forms where the female often becomes so 



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