Miscellaneous. 477 



Oa the Development of the Branchial Povxhcs and Aortic Arches in 

 Marine Turthi^, from Investigations upon Embryos of Chelonia 

 viridis. By Dr. J. F. vax Bemmelen, of Batavia. 



1. Tho earliest rudiments of the branchial pouches and aortic 

 arches in turtles entirelj' agree with those found in lizards and 

 snakes; their subsequent development, however, pursues a different 

 course, and is more in accordance with the conditions observed in 

 birds than with those exhibited in the case of the other reptiles. 



2. As in the last-mentioned animals, the rudiments of five 

 branchial pouches and six aortic arches are primitively formed. 

 Besides these, on the posterior wall of the hindcrmost branchial 

 pouches, where the branchial section of the gut narrows to form the 

 pharyngeal portion, an additional pair of pouch-shaped evaginations 

 are developed, jiLst as the same process takes place in snakes. They 

 lie to the right and left in the region in question, where in lizards 

 there arises on one side only, namely on the left, an epithelial 

 evagination, which becomes constricted olF in the form of a vesicle 

 previously termed by me the " supra-pericardial body " (" Supra- 

 pericardialkorperchen "), since I regard it as homologous with the 

 derivatives of the branchial gut in the Selachians, upon which I 

 bestowed the same designation. 



3. The three foremost branchial pouches are undoubtedly open 

 during a short time. Whether this is also the case with regard to 

 the two hindermost ones I cannot definitely say, but it appears to 

 me to be probable with respect to the fourth branchial pouch. 



4. As in the Amniota, the tuha Enstachii arises from the dorsal 

 portion of the first branchial pouch : its external aperture soon closes 

 again, while the tympanic cavity does not develop until much later. 



5. The second branchial pouch lies close behind the first ; the 

 portion of the branchial gut separating the one from the other 

 possesses a wider lumen than the section following further towards 

 the rear. The dorsal apex of the second branchial pouch expands 

 into a follicle-shaped epithelial bud; this, however, does not become 

 constricted off, as in the case of the lizards, where it forms the first 

 (foremost) lobe of the thymus. Neither does the second branchial 

 cleft become entirely constricted off" from the branchial gut, to 

 remain as an epithelial vesicle lying in the midst of tho connective 

 tissue of the neck, as in the case of the snakes. In the subsecjuent 

 development of the embryo the second branchial pouch simply 

 becomes aborted, as in the 1)irds. 



6. The cleft-shaped external apertures of the foremost branchial 

 pouches undergo, as in the case of birds, a considerable backward 

 movement. This shifting of position is occasioned by the backward 

 outgrowth of the branchial arches, which consequently commence 

 to cover one another in imbricated fashion. The second branchial 

 cleft in particular undergoes so nuich backward dis])lacenient that 

 the corresponding branchial pouch becomes ^really elongated in the 



