DEVELOPMENT OF PHRYGANIDS. 599 



EXPLANATION OF PLATES XXXVL4, XXXVIb, 

 XXXVIc. 



Illustrating Mr. W. Patten^s paper on "The Development of 

 Phryganids, with a Preliminary Note on the Development 

 of Blatta Germanica/' 



List of Reference Letters. 



am. Amnion, an. Anus. at. Antenna, b. cv. Body-cavity, bd. Blasto- 

 derm, bl. Blastema, br. Brain. cm. Cross commissures, d. o. Dorsal 

 organ, ee. Ectoderm, en. Endoderm. f.hd. Forehead, ht. Heart. I. cm. 

 Long commissures, md. Mandible, mp. v. Malpighian vessels, ms. Meso- 

 derm, mx.^ and mx."^ Maxillae 1 and 2. n.f. Neural furrow, ce. (Esophagus, 

 f.'^^ Thoracic appendages, pel. Procephalic lobes. /;/•. Proctodaeum. 

 sl.g. Salivary glands. sp.g. Spinning glands. sr. Serosa. tr. Trochee. 

 V. p. Ventral plate, y. c. Yolk-cells, gti. Ganglion. 



PLATE XXXVIa. 



Fig. 1. — Lateral view of the egg in the blastoderm stage. 



Fig. 2. — Same view of the egg four hours later, showing the thickening of 

 the blastoderm to form the ventral plate. 



Fig. 3. — Lateral view of the ventral plate during the formation of the 

 embryonic membranes. It is shown as a semi-transparent mass of cells; the 

 headfold at am., and tailfold at a. 



Fig. 4.— Same embryo one hour later, the head and tailfold have approached 

 each other preparatory to uniting. 



Fig. 5. — Dorsal view of the anterior end of the embryo. The amnion and 

 germinal band are seen in optical section, gst, gastrula invagination. 



Fig. 6. — Same view of the embryo, after the gastrula invagination has dis- 

 appeared. The embryo has increased in length, so that the ventral plate 

 extends the whole length of the egg. At a is a segmentation furrow dividing 

 the yolk into halves. 



Fig. 7. — Lateral view of the embryo, seen from the left side. None of the 

 appendages have as yet appeared. 



Fig. 8. — The same embryo twenty-four hours later, showing the first ap- 

 pearance of the appendages. 



Fig. 9. — Same embryo, two days later than that represented in Fig, 7. 

 The ventral plate is seen to be continuous with the amnion at both extremities 

 of the body, am} and am.'^ 



