460 PATTEN AND HAZEN. [Vol. XVI. 



I. Introduction. 



The work described in the following pages was mainly done, 

 during the year 1895 and 1896, in the Biological Laboratory 

 of Dartmouth College, and was continued through the summer 

 season of 1896 in the Marine Biological Laboratory at Woods 

 Roll. 



The problem we had in mind at first was the development of 

 the branchial cartilages, but it was finally deemed advisable to 

 work out, in connection with this problem, the development 

 of the genital ducts and the " coxal gland," or nephridia, as all 

 three of these organs are closely associated with one another 

 during development. 



We were in a certain measure prepared for the independent 

 origin of the nephric lobes and nephric duct by the discovery 

 that in the adult kidney, as seen by the aid of injections, a 

 distinct nephric duct is present, which could hardly be anything 

 else than the tube seen by other investigators in the embryos. 



This left the development of the nephric lobes to be accounted 

 for in some other way than as a modification of the embryonic 

 duct. 



We are indebted to Professor Whitman for the privileges of 

 the Marine Biological Laboratory at Woods Roll and to Dr. 

 William A. Redenbaugh for assistance in working out the 

 course and origin of the nerves found in the region of the 

 nephridial lobes. 



n. Methods. 



The embryological material was killed either in Perenyi's 

 fluid, picro-nitric acid, picro-sulphuric acid, corrosive sublimate, 

 or formalin. The most satisfactory results were obtained with 

 Perenyi's fluid. The embryos remained in it overnight. In 

 the morning the much distended membranes could be easily 

 removed, and the eggs placed at once in large quantities of 

 95fo alcohol, which was changed often to prevent the yolk from 

 swelling and cracking. Low grades of alcohol must be avoided 

 in the preliminary stages of hardening. 



