404 EDGAR J. ALLEN. 



wards found to hatch equally well in a stream of running sea 

 water, and this method was then chiefly used. 



Towards the end of the summer, larvae in all stages of 

 development were obtained in large numbers by fishing with 

 a fine net in certain sheltered pools, and further breeding in 

 captivity became unnecessary. 



The larvae were preserved in Flemmiug's fluid (both the 

 weak and strong mixtures gave good results), washed in water, 

 and hardened in alcohol. The sections were stained with 

 Delafield's haematoxylin. 



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 antennae, and the shell-glands, which open 

 at the bases of the second maxillae. 



The Green Gland. — A horizontal longitudinal section 

 through the green gland of a Palaemonetes larva, which is 

 three or four days old, is represented in fig. 1. At this stage 

 the gland has a form which is similar to that described by 

 Weldon (No. 20) and Marchal (No. 17) as persisting in the 

 adult of Virbius, Pandalus, and Crangon, excepting that 

 there is as yet no trace of the remarkable enlargement of the 

 bladder which the former author designates as '' uephro- 

 peritoneal sac." 



The end-sac (fig. 1, e. s.) communicates by means of a 

 U-shaped tube {tu.) with the bladder {bl.), which is in reality 

 merely the enlarged distal portion of the tube. (The dotted 

 lines in the figure [fig. 1] indicate the way in which tube and 

 bladder join each other, as determined by the following sec- 

 tions of the series.) The bladder is placed in communication 

 with the exterior by means of a very short ureter, which opens 

 in the region indicated by the letter in fig. 1. 



It is not necessary for me to give an account of the histolo- 

 gical structure of the various portions of the gland, as it has 



