538 



MERISTIC VARIATION. 



[part I. 



C. Antenna}. 



*82S. Palinurus vulgaris : right antenna bore three complete 

 filaments. So far as last spiny joint (merocerite) normal. Of 

 this joint the peripheral portion 

 much enlarged, presenting two 

 articulations. The most posterior 

 bore a normal carpocerite and fila- 

 ment (Fig. 196, 1). The anterior 

 articulation bore a double carpo- 

 cerite with two filaments (II and 

 III). As author points out, II is 

 structurally a left antenna. [By 

 the kindness of M. Alphonse Milne 

 Edwards I have been allowed to 

 examine this specimen. I am not 

 sure that I succeeded in correctly 

 determining the surfaces of the 

 extra antennae, for the basal parts 

 were not veiy fully formed ; but 

 according to my determination 



their relations differed markedly „,«„„., . , 



r ,1 r f»j_i o l- j.* Fig. 196. Proximal parts of the right 



from those of any of the Schematic antenna of Pa Unurm vulgaris, No. 828. 



positions, for while the position I, the normal. II, extra left. Ill, extra 

 of origin is VVA the two extra ri g ht - ( After L eg er 

 antennae stand very nearly in the Position DA.] 

 sci. nat, ZooL, 1886, S. 7, i. p. 109, PI. 6. 

 *829. Astacus fluviatilis : exopodite of left 

 antenna (Fig. 197) bears two supernumerary 

 points, R' and L', which seem to have been 

 inserted upon the internal border of the 

 normal exopodite. Stamatt, G., Ball. Soc. 

 Zool. France, 1888, xm. p. 199,^. 



Amorphous Cases. 



As has been stated, there are many cases, 

 recorded or preserved, in which the nature of 

 the parts cannot be made out. The majority 

 of these are, I believe, injured or deformed 

 limbs, and not cases of repetition of parts. 



Nevertheless of the latter class there are un- tiUs paving extra points to 



, exopodite of left antenna. R, 



doubtedly some amorphous cases, though they normal right. L, normal left. 



are far less common than regular ones, even R', L', extra right and left. 



as normal structures are more common in their (After Stamati.) 



regular shapes than in a deformed state. I mention the following as 



being, I think, the earliest record of abnormalities of this class. 



830. Homarus : left chela having irregular process on inner border of 



dactyl opodite, and two irregular processes on inner border of index. 



[No description.] Bernhardus a Berniz, Miscell. Curios., Jena, n. 



1671, p. 175, Obs. ci. PI. 



L£ger, A 



nn. 





Fig. 197. Astacus fiuvia- 



