In a former paper I traced the development of Julus terrestris from the ovum within the ovary up to the bursting of the shell and the liberation of the young animal on the twelfth day. In the present paper I propose to take the different organs one by one, and to describe their development. This different way of treating the subject seemed to me to be the best: firstly, on account of the difficulty of describing a long and complicated development like that undergone by Julus in its larval life by dividing the history of its growth into periods of time; and, secondly, on account of the nature of the work which has hitherto been done upon this subject. The two most important works bearing on the subject of my paper are those of Newport (13)* and Metschnikoff (12). The former has observed the general development of Julus terrestris , and has given us a most accurate and full description of the external features of the young animals at various stages, from the time of hatching almost up to the adult condition.