CHAP. IY. MELITA MESSALINA. 29 



of this contrivance, or that the latter would rather be 

 injurious than beneficial to other species, its presence 

 only in these few Amphipoda will have to be regarded 

 not as the work of far-seeing wisdom, but as that of a 

 favourable chance made use of by Natural Selection. 

 Under the latter supposition its isolated occurrence is 

 intelligible, whilst we cannot perceive why the Creator 

 blessed just these few species with an apparatus which 

 he found to be quite compatible with the " general plan 

 of structure " of the Amphipoda, and yet denied it to 

 others which live under the same external conditions, 

 and equal them even in their extraordinary salacity. 

 Associated with, or in the immediate vicinity of the 

 two species of Metita, live two species of Allorchestes, 

 the pairs of which are met with almost more numerously 

 than the single animals, and yet their females show no 

 trace of the above-mentioned processes of the coxal 

 lamellae. 



These cases, I think, must be brought to bear against 

 the conception supported with so much genius and 

 knowledge by Agassiz, that species are embodied 

 thoughts of the Creator; and, with these, all similar 

 instances in which arrangements which would be equally 

 beneficial to all the species of a group are wanting in 

 the majority and only conferred upon a few special 

 favourites, which do not seem to want them any more 

 than the rest. 



