DEVELOPMENT OF SUPRAPERICARDIAL BODY 385 



It is a single vesicle, partly embedded in the pharyngeal epi- 

 thelium. Its lumen does not communicate with the cavity of 

 the pharynx (fig. 7). The left gland, shown in figures 7 and 2(3. 

 is connected to the pharyngeal epithelium by three small tubules. 

 The connecting-stalk has developed into a branching mass of 

 tubules, a few of which apparently anastomose. The distal 

 portion of the gland forms an elongated, obliquely placed vesicle, 

 directed cranially. It gives rise to a few secondary tubules 

 along its margins and dorsal surface. It is fused with some of 

 the tubules immediately dorsal to it, but has an independent 

 lumen. 



In embryos of the 'pup' stage (20 to 22 cm. in length) and in 

 the newborn and adult the gland is easily found by dissection 

 under the binocular microscope. Although many specimens were 

 examined, particularly of the 'pups,' the right gland was never 

 found in these older stages. Upon removing the dorsal pharyn- 

 geal wall the position of the left gland is indicated by a small pit 

 in the floor of the pharynx just lateral to the cardiobranchial 

 (basibranchial) cartilage. Figure 29 is a cleared dissection of 

 the head of a 'pup' 21 cm. long, showing the gland in situ. 

 The ventral muscles, heart, and a portion of the pectoral girdle 

 have been removed, as well as the dorsal musculature of the 

 head and dorsal wall of the pharynx. The body or main portion 

 of the gland lies between the cardiobranchial cartilage and the 

 fifth arch of the left side. It is partly covered at its base by 

 the ceratobranchial cartilage and the caudal portion of the 

 coracobrachial muscle. 



The caudal half of this gland was reconstructed and is shown 

 in figure 27. The dorsal part of the connecting-stalk is broadly 

 attached to the pharyngeal epithelium and has a deep blind 

 pit in its center. Its ventral portion is solid and fuses with 

 some of the adjacent tubules. "When compared with the gland 

 in the 95 mm. embryo it is found that the entire gland has greatly 

 increased in size. The large ventral mass of tubules and vesicles 

 has become relatively farther removed from the pharyngeal 

 epithelium. The connecting-stalk is single and much longer, 

 and appears to be a direct outpouching or diverticulum from 



