236 iMr. E. J. Allen on the Nephridia and 



XL. — Preliminary Account of the Nephridia and Body- 

 Cavity of the Larva of Pal£emonetes varians. By Edgar 

 J. Allen, BSc, University College, London*. 



The researches of which the present communication contains 

 a brief summary were carried on during the summer of the 

 present year at the Laboratory of the Marine Biological Asso- 

 ciation in Plymouth, where I occupied a table by appointment 

 of the British Association Committee. The observations were 

 made chiefly on larva of PaJcemonetes varians, but other species 

 have also been included, and will be mentioned in particular 

 instances. 



I. The Nephridia. 



During the greater part of the larval life two pairs of 

 nephridia are present — the green glands, which open at the 

 bases of the second antenna?, and the shell-glands, which open 

 at the bases of the second maxillae. 



The Green Gland. — In a larva of Palwmonetes which is a 

 few days old the green gland has a form similar to that 

 described by Weldon f and Marchal \ for the adult of Virhius, 

 Pandalus, and Crangon, excepting that the remarkable 

 enlargements of the bladder, which the former author has 

 termed " nephroperitoneal sacs," are not as yet developed. 

 The gland consists of an end sac, which communicates by 

 means of a U-shaped tube with a very short ureter opening 

 at the base of the antenna. The distal portion of the tube is 

 slightly enlarged, and may be called the bladder. At the 

 time of hatching of the larva the whole gland consists of a 

 solid mass of cells, in which no cavity has appeared, although 

 the portions which afterwards form the end sac and the tube 

 can be distinguished, and the ureter and external opening are 

 already present. Shortly after the larva has become free the 

 cells separate and give rise to the lumen of the gland. 



The later development of the green gland consists chiefly 

 in the enlargement of the bladder, which grows at first inwards 



* From the ' Proceedings of the Royal Society,' vol. lii. no. 318, 

 pp. 338-342. 



t Weldon, W. F. R., "The Renal Organs of certain Decapod Crus- 

 tacea," Quart. Journ. Micr. Sci. vol. xxxii., 1891. 



X Marchal, P., " Recherches anatomiques et physiologiques sur I'appa- 

 reil excr(5teur des Crustac^s Ddcapodes," Arch. Zool. exp6r. vol. x., 18U2. 



