Plate XXVI. 



Fig. 39. Sec. No. 384. G. X3. The mass of contributed cells is much larger 

 in proportion to the size of the general visceral component, than in the preceding 

 figure. 



Fig. 40. Sec. No. 386. G. X3. The placode is quite marked and there is active 

 proliferation and an extensive contact area. 



Fig. 41. No. 390. G. X3. This section shows the placodal thickening persisting, 

 even to the posterior extremity of the ganglion, where there is only a slight area 

 of contact. 



Fig. 42. Sec. No. 410. G. X4. The apparently large size of the mass of contrib- 

 uted cells is probably exaggerated as a result of the peculiar form of the ganglion 

 at this point. There is evidence of active proliferation but only a short area of 

 contact. 



Fig. 43. Sec. No. 410. G. X4. An outline drawing of the same section as shown 

 in Fig. 42, showing the relation of the placode to other structures. This mag- 

 nification does not reveal the contact. 



Fig. 44. Sec. No. 412. G. X4. Showing the extensive contact and the large 

 size of the mass of contributed cells. 



Fig. 45. Sec. No. 413. G. X4. The placode is quite distinct from the other 

 ectodermal thickenings. 



Fig. 46. Sec. No. 413. G. X4. A high power drawing of the same section as 

 shown in the preceding figure, showing evidence of active proliferation. The 

 outline of the general visceral ganglion is fairly distinct. 



Fig. 47. Sec. No. 415. G. X4. Contact between the placode and the ganglion 

 no longer exists but the placode is very large. 



Fig. 48. Sec. No. 418. G. X4. Showing partial detachment by lamellation, of 

 the placodal mass from the ectoderm. 



Fig. 49. Sec. No. 415. G. X4. A high power drawing of the same section as 

 shown in Fig. 47, showing a large mass of cells contributed by the placode but not 

 yet metamorphosed. The outline of the general visceral component is fairly 

 distinct and the nuclei of the placodal cells are slightly smaller than those of the 

 general cells. 



Fig. 50. Sec. No. 420. G. X4. The placodal component is relatively small and 

 a portion of the placodal mass is partially detached from the ectoderm by 

 lamination. 



Fig. 51. Sec. No. 329. G. Xi. A section of the first division of Gang. X, three 

 sections posterior to that shown in Fig. 24. 



Fig. 52. Sec. No. 428. G. X. Showing the general topography and the 

 posterior extension of the main ganglionic mass of Gang. X, as it comes into con- 

 tact with the ectoderm in the post-branchial groove. 



