CRUSTACEA MALACOSTRACA. III. ^3 



as Racovitza thinks, a separate joint, the prsecoxa. My interpretation in 1890 of the three lamellar 

 expansions in the female maxilliped is certainly correct And my opinion is corroborated by the struc- 

 ture of the maxillipeds in the male and the ovigerous female of Mesidothea Sabini Kr. and Astacilla 

 granulata G. O. Sars, both studied later on and figured on PI. XV. 



In 1893 I wrote (in "Zool. Anz." No. 420): "Es folgt aus dass man drei Glieder im Stainm 



von alien gespaltenen Gliedmassen als ein primares Verbal tniss ansehen muss"; on p. 9 in the present 

 paper are briefly summed up most of the cases, where three joints, consequently also a prsecoxa, are 

 still extant. Therefore Racovitza's interpretation of the proximal elements in the female maxilliped 

 of Sphceromides would have been most welcome, if I had been able to find it correct. — Fortunately 

 I can adopt another proof given by him of my theory on three joints in the sympod of the appen- 

 dages in Crustacea. 



In 1902 Bouvier pointed out the existence of three joints in the peduncles or sympods of the 

 pleopods in the genus Bathynomus. In 1903 I confirmed Bouvier's discovery and said: "The gigantic 

 animal is an excellent object for the study of the joints in the sympods of pleopoda, while such joints 

 in animals of normal size are difficult to discover and especially difficult to judge of with certainty". 

 In 1912 Racovitza described and figured (op. cit. p. 294 — 95, figs. VII and VIII) three joints in the 

 sympod of first pair of pleopods in the moderately large animal Spharomides Raymondi Dollf. (length 

 24 mm.), but his statement: "Hansen ne trouva cependant qu'uu seul article chez routes les especes 

 qu'il etudia", is extremely misleading, which is easily seen from the quotation just given, together 

 with the fact that in my earlier main paper on Cirolana etc. I said nothing on the morphology of the 

 pleopods. I have never said that I had only found a single joint in the sympod of the pleopods in 

 Cirolaninse or any other animal of malacostracous Crustacea; at least in many and probably in most 

 Malacostraca exceeding a few millimeters in length two joints can be seen without much difficulty, 

 but according to my theory the sympod shall be composed of three joints, and for various reasons 

 it will generally be either difficult or impossible to point out their elements; besides, I had never made 

 a closer investigation of the sympods of the pleopods in selected types of Cirolana or other Isopoda 

 or in various types of Malacostraca. Now I have examined first pair of pleopods in Cirolana borcahs 

 and a few species of s£ga, and have been able to find chitinized elements of the three joints in question. 



Fig. 6 a on PI. XIV represents the left half of the first abdominal sternite (si) with the sympod 

 and the proximal part of eudopod (en) and exopod (ex) of first pleopod, seen from below, of JEga 

 arctica Littk. The third joint (j.) of the sympod is firmly chitinized, while first and second joints are 

 thin-skinned with chitinous plates as remnants of the joints. Second joint shows a long transverse 

 plate (2 o) reaching the outer margin and divided into two pieces, and a small plate (2 i) at the inner 

 margin. First joint has a somewhat large transverse plate (/ 0) reaching the sternite, while at its inner 

 angle a very firm subquadrangular plate (/ i) is seen, which is deeply cleft in the median line and, 

 according to my opinion, consists of the inner part of first joint of both pleopods of first pair, and 

 these two parts are fused at the base. As the pleopods of same pair are moved simultaneously, this 

 fusion of their inner basal part must give strength and uniformity to their movement - - The struc- 

 ture of the sympods of first pair of pleopods in Cirolana borealis Lilljeb. (PI. XIV, fig. 4 a) is some- 

 what similar to that in sEga arctica, but the plates of first and especially of second joint are more 



