History of British Entomostraca. 317 



than twenty days, andin a series of very careful experiments whichhe 

 made in February and March, he found it to occupy twenty-eight 

 days. For the first eight days, they underwent little or no change 

 — between the eighth and thirteenth the body appeared a little more 

 elongated — between the thirteenth and nineteenth, the line of demar- 

 cation between this increase of length and primitive size was trace- 

 able by a line of a brown colour, and the insect had acquired a third 

 pair of feet — between the nineteenth and twenty-fifth, nogreat change 

 took place, only the third pair of feet were more developed — between 

 the twenty-fifth and twenty-eighth the first moulting took place 

 — and thirteen days afterwards they moulted a second time. In a 

 series of experiments which I undertook, upon the same species, in 

 the end of June and beginning of July, when the thermometer was 

 frequently above 80° during the day, I found the time occupied in 

 the process, in some instances, very much shortened. In one brood 

 which were hatched on the 21st of June, I found some had com- 

 pleted their first moulting on the 1st of July, or on the eleventh day. 

 In another brood hatched on 22d June, I found the same result, se- 

 veral of the young having undergone a first moulting on the 2d July. 

 On the 4th I could only see one that had not moulted — and next 

 day, the 5th, this one had also undergone the change : the second 

 moulting in many of them took place only a few days after the first. 

 In another brood hatched a little earlier in June when the weather 

 was not so hot, I found the changes take place as follows : When hatch- 

 ed the insect appeared of an oval shape, (Plate VIII. Fig. 9,) having 

 two thick antennae of three articulations each; two pairs of feet, bifid 

 at extremity ; in the upper pair, one division consisting of two and the 

 other of only one articulation; in the lower, both divisionshavingonly 

 one articulation ; extremity of body furnished with two short setae on 

 each side. On the eighth day, the body is considerably elongated, and 

 a distinction has begun to be perceptible between this increase and 

 original size, with some appearance of setae where the third pair of feet 

 afterwards appear ; intestine very distinct, (Fig. 10.) On the fif- 

 teenth day, the third pair of feet have become distinctly formed ; the 

 lower part of body more elongated, the elongation marked by an- 

 other line of demarcation ; the setae on the edges of the antennae have 

 become visible, and those of the feet longer and more numerous, 

 whilst the second pair of feet have the upper division of two articu- 

 lations, (Fig. 11.) On the seventeenth day, moulting has taken 

 place — the body is divided into two segments ; tail into three ; the 

 terminating one cleft at extremity, each cleft sending off a long seta; 

 antennae of about six articulations ; the antennules have become dis- 

 tinctly visible, and the feet have assumed the appearance they after- 



