338 Mr. E. J. Allen. On the Nepliridia and Body [Dec. 8, 



IV. " Preliminary Account of the Nephridia and Body Cavity 

 of the Larva of Pa/cemonetes varians." By EDGAR J. 

 ALLEN, B.Sc., University College, London. Communicated 

 by Professor W. F. R. WELDON, F.R.S. Received Novem- 

 ber 17, 1892. 



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 Association in 

 Plymouth, where I occupied a table by appointment of the British 

 Association Committee. The observations were made chiefly on larvae 

 of Palce.monetes 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 

 antennse, and the shell glands, which open at the bases of the second 

 maxillae. 



The Green Gland. In a larva of Palcemonetes which is a few days 

 old, the green gland has a form similar to that described by Weldon* 

 and Marchal| for the adult of Virbius, Pandalus, and Crangon, except- 

 ing 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 L)' sna P e d 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, towards 

 the middle ventral line of the body, then upwards, within the ceso- 

 phageal nerve ring, and anterior to the oesophagus, to the middle 



* Weldon, W. F. "R., "The Renal Organs of certain Decapod Crustacea." 

 'Quart. Journ. Micr. Sci.,' vol. 32, 1891. 



f Marchal, P., "Recherches anatomiques et physiologiques sur 1'appareil ex- 

 creteur des Crustacea Decapodes." 'Arch. Zool. Exper.,' vol. 10, 3892. 





