CKt STACKA MAI.AC08TRACA. III. 



tat Racoviua thinks, a separate joint, the pnecoxa. My interpretation in 1890 of the three lamellar 

 expansions in the female tnaxilliped is certainly correct And my opinion is corroborated by the .true- 

 turf of the maxillipeds in the male and the ovigerous female of Mrsidotkea Sabini Kr. and AtlatMa 

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



In 1893 I wrote (in "ZooL Anz." No. 430): Es folgt aus . . . . dass man drei (Mieder im Summ 

 vm alien gespaltenen Gliedmassen als ein primares Verhaltniss anseheu nuiss"; on p. 9 in the present 

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

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

 of Sphrromidts 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 discover, 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. 29495, figs. VII and VIII) three joints in the 

 -\inpod of first pair of pleopods in the moderately large animal Sphtrromidat Haytnondi Dollf. (length 

 ^\ mm.), but his statement: "Hansen ne trouva cepcndant qu'un seul article chez routes les cspeces 

 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 

 Cm'l.uiiii.i- 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 borralu 

 and a few species of Alga, 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 (st) with the sympod 

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

 irctica Lutk. 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 (jo) reaching the outer margin and divided into two pieces, and a small plate (ji) at the inner 

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

 angle a very firm subquadrangular plate (//) 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 oorcalis Lilljeb. (PI XIV, fig. 4 a) i some- 

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



