Linihs and Mouth-parts of Crustaceans and Insects. 419 



have myself also seen lohat is asserted', besides this I have 

 several times refrained from giving a quotation when it 

 appeared to me to be entirely unnecessary or when an author 

 could not be quoted without lengthy explanations. Certain 

 of the statements alluded to are already to be found in my 

 memoir in " Dijmphua-Togtet &c." (especially in the Frencli 

 resume of the paper), and are there accompanied by figures; 

 in " Cirolanidfe .... Musei Haun." some unimportant 

 corrections are 2:iven. 



1. GENERAL OBSERVATIONS. 



1. It is probable that the appendages of the Crustacea 

 primitively consist of an axial portion and two equivalent 

 rami. On practical grounds, however, I employ the term 

 endopodite for the axial portion and inner ramus, so that 

 the outer ramus is considered as proceeding from one of the 

 joints of the endopodite. 



2. By comparison of the limbs of the Aranea, Thehj- 

 phonus, Scorpiones, Chelonethi {Chelifei — Obisium) , and 

 Solifugae we soon discover that the segments, with the excep- 

 tion of the two first, are not homologous one with another 

 according to their parallel numbers (Gaubert). In order to 

 determine the homology enumeration is not sufficient ; we 

 must in addition examine the form and length of the segments 

 and especially the direction and form of the articulation. 

 This conception, the correctness of which can easily be 

 perceived in the case of Arachnida, is utilized in the case of 

 the malacostracous Crustacea to deduce new results (§ 22). 



,'}. If we would arrive at a comprehension of the mouth- 

 parts and limbs of Insects, Myriopods, and Crustaceans from 

 a really morphological point of view, we must first study 

 them in different types belonging to the last-mentioned class. 



4. In order to understand the structure of the maxilla in 

 the Malacostraca we must commence with the raaxilli pedes. 

 For instance, in the case of the Isopods and Amphipods it is 

 easy to see that the raasticating-lobes, which arise from the 

 inner side of the second segment or (in Gammarinie) from 

 the second or third segment, are simple processes starting 

 from the inner angle of the respective segments ; in Earycope, 

 for example, a lateral masticating-lobeof this kind is a simple 

 prolongation, while in Idothea entomon, on the other hand, it 

 is divided off by a secondary articulation which has a certain 

 power of movement {vide " Dijniphna-Togtet," tab. xx.). 

 Similarly the masticating-lobes of tlie two j)airs of maxillaj 

 must be rt-garded as processes from the sides of the several 



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