folsom: mouth-parts of anurida maritdia. 91 



last five abdominal segments, and by longer appendages, of which the 

 antennae and legs show traces of segmentation. It is approximately 

 the stage of Figures 42 and 47 of Claypole. 



At Stage 3 (Plate 1, Figure 3) the ventral surface of the embryo is 

 almost flat, preparatory to involution ; the legs are decidedly longer, 

 and the fundament of the proctodteum is distinct. Figures 43 and 

 43' of Claypole belong near this stage; also Figure 10 of Ryder ('86), 

 likewise for Anurida maritima. 



During Stage 4 (Plate 1, Figure 4) the germ band is folding into the 

 yolk, the fold beginning anteriorly and continuing backward. The 

 antennae and legs are long and stout. My figure shows a stage a little 

 later than that of Figure 44 by Claypole. 



At Stage 5 (Plate 1; Figure 5) the involution has reached the centre 

 of the egg, the antennae and legs are distinctly segmented, the mouth- 

 folds are conspicuous, and the dorsal organ has shrunken considerably. 



Stage 6 (Plate 1, Figure 6) is much like the last, except that the 

 head and tail of the embryo have approached each other. The dorsal 

 organ is much reduced and somewhat flask-shaped. This is the stage 

 of Ryder's Figure 7. 



At Stage 7 (Plate 2, Figure 7) the eyes are first recognizable as five 

 black circular patches on either side. Figure 45 of Claypole represents 

 this condition. 



Stage 8, which 1 have not figured, differs externally from the last in 

 that the number of eyes is no longer evident, it being obscured by a 

 suff'usion of pigment. The degenerating dorsal organ now disappears by 

 resorption. 



Stage 9 (Plate 6, Figure 41 ; also Claypole, Figure 48) refers to the 

 newly hatched insect. Before this period, movements of the insect may 

 be seen through the egg membranes. If eggs have been kept dark, — 

 the normal condition, — the emerging insects are white, excepting the 

 eyes ; if exposed to sunlight, however, the embryos become blackish- 

 blue long before hatching. At emergence the external clothing of setae 

 is complete^ and the mouth-parts are fully formed. 



Procephalic Lobes. 



The fundaments of the procephalic lobes are two isolated thickenings 

 of the blastoderm, which are the first of the paired fundaments to ap- 

 pear. Each procephalic fundament is lenticular in form and rapidly 

 increases in thickness and area. In the earlier stages the procephalic 



