162 



The Coelom and Nephridia of Palaemon serratus. 



By 



W. F. R. Welflon, M.A., 



Fellow of St. John's College, Cambridge ; Lecturer on Invertebrate Morphology in 



the University. 



With Plates XIII— XV. 



The accepted accounts of the excretory organs of the Decapod 

 Crustacea are based chiefly upon the investigations of those numerous 

 observers who have studied Astacus fluviatilis ; the only recent memoir 

 which attempts to deal with the arrangement of this system of organs 

 in any other genus being the well-known work of Grobben.^ 



Dr. Grobben gives a short description of the nephridium of 

 Palcemon Treillianus, which may be summarised as follows : 



The whole organ he believes to consist of a single tube, beset 

 with numerous caecal diverticula, and arranged for the most part in 

 a compact coiled mass, which forms the glandular portion of the 

 kidney. The outer end of this tube dilates into a large bladder, 

 which leads by a short and delicate ureter to the exterior ; while its 

 inner extremity terminates in a curious enlargement, the " end-sac," 

 the walls of which are richly supplied with blood-vessels. 



This account of the structure of a Decapod green gland is very 

 attractive, because of its complete agreement with the descriptions 

 given by Claus, Grobben, Hoek, and others of the shell-gland of 

 the Entomostraca, and it has naturally received much attention from 

 morphologists. Lankestert has compared the " end-sac " of the 

 Crustacea with the space into which the nephridium opens in an 

 embryo Limulus, and has suggested that in each case the vesicle 

 which receives the termination of the renal tubule is a reduced re- 

 presentative of the coelom ; and Sedgwick has demonstrated that the 

 similarly circumscribed space into which each nephridium of Peripatus 

 is the remnant of an embryonic coelomic pouch. J 



* Grobben, Die Antennendrilse der Crustaceen, Arb. Zool. Inst. Wien, Bd. iii, 1880. 

 The references to the earlier works are so fully given in this paper that they will not be 

 repeated here. 



t Quart. Journ. Micr. Sci., vol. xxv, 1885, p. 516. 



;}; Sedgwick, A Monoqravh of the Develovment of the Qenus Peripattis, Studies from 



