476 MALL. [Vol. V. 



shape, as shown in the figure. It is in general parallel with the 

 alimentary canal and rests wholly between the fourth and fifth 

 aortic arches. 



The thyroid gland is as a small nodule lying in the median 

 line on the ventral side of the second branchial arch. 



Throughout their whole extent the branchial pockets at no 

 point communicate with the exterior of the body. In no sec- 

 tion is there a rupture of the membrane of His. 



Immediately behind the branchial region the embryonic phar- 

 ynx gives off the larynx, which farther back divides into the 

 two bronchi. The intestinal tube now becomes dilated to 

 form the stomach, below which arise the sprouts to form the 

 pancreas and liver. The pancreas is composed of a small group 

 of cells which lie in the mesogastrium, contains a lumen and 

 communicates directly with the duodenum. 



On the ventral side, however, this sprout is irregular, one 

 branch boring into the liver, and the other ending as a sphere 

 in the septum transversum. The liver is composed of two 

 lobes, the right being about i mm. in diameter and half a 

 millimetre thick. Its lateral border is symmetrical, and on its 

 median side it is convex. It communicates along the septum 

 transversum to the left lobe, which is very regular in shape. 



Behind the liver the intestine makes an irregular curve 

 towards the umbilical cord and to the left, and finally ends in 

 the cloaca. 



The cloaca is pyramidal in shape, with the apex pointing 

 towards the tip of the tail. The highest point of the apex is 

 blended with the ectoderm, and no doubt is about to break 

 through. The intestine enters on the oral side of the base 

 (speaking of the cloaca as a pyramid), and the allantois arises 

 somewhat more aboralwards. The allantois is a small tube 

 which is markedly dilated as it enters the cord, and then again 

 becomes more constricted. On either side of the allantois and 

 on the dorsal side of the intestine the Wolffian duct enters. 

 Shortly before the duct enters the cloaca it gives off a blind 

 tube, the beginning of the kidney. 



The Wolffian body is a very large, somewhat lobulated body 

 extending on either side of the intestine from the cloaca to the 

 sixth dorsal nerve. Its general outline is given in Fig. 2, PI. 

 XXX. Upon transverse section, its free surface is small and 



