731 



size, but is more compact; owing (o the fact that it has finer lymph- 

 spaces than the thjrans. No trace of such a body was to be found 

 at the S''*, 4"', 5"^ and 6"' tiiymomere. 



The suprapericardinl body was discovered by van Bemmelen ') 

 (1885) at the end of the branchial gut. Later it was found in all 

 classes of vertebrates. It is generally taken as the last indication of 

 an abortive branchial pouch, and mostly appears on only one side 

 of the body. 



In 1906 Bhaus found it in the 67 m.m. long embryo of Heptan- 

 chus, which very likely originates from the same mother-animal as 

 mine, and 1 can corroborate his statement. It is only well developed 

 in the left half of tiie body, and shows itself as a little bladder, 

 the lumen of which is encircled by a single layer of fairly columnar 

 epithelium cells. It is to be seen on 35 sections, and is situated as 

 Bhaus stated, behind the last visceral arch, in the angle which this 

 makes with I he ceratobranchial. Just as Bhaus, 1 found if near its 

 posterior margin connected with the epithelium at the base of the 

 branchial gut by a short pedicle. 



On the right side the organ is rudimentary. 



1 found it represented by a flattened little group of epitlielial 

 cells without a lumen, and totally severed from the gut epithelium. 

 This is visible in the sections passing through the posterior half of 

 the vesicle on the left. Bhaus does not mention this little group. 



His specimen was probably somewhat further developed than mine, 



1) Owing to the presence of a suprapericardial body in the embryos of Heptanchus 

 (van Bemmelen in vain souglit for it in the adult animal I one cannot assume that, 

 in higher animals, this little body is the remains of a branchial cleft, which is 

 present in the Notidanides as such. The morphological significance of this organ 

 is a problem One may of course believe that it is the remains of a branchial cleft, 

 which still lies further caudally than the last (Stl') of Heptanchus. Braus e. g. 

 takes it to be the rest of a lO'ii branchial pouch. 



He professes to find tlie remains of a (9^'') branchial poucli in a slight 

 protrusion of the intestinal wall behind the last branchial arch, in llie angle 

 between the last ("fi') ceratobranchial, and a caudalwaids directed protuberance 

 on its ventral side. 



Although this protuberance cliondrifies continuous with llie 7''i ceratobranchial, 

 he considers it to be the remains of an 8'!' branchial arch. 



1 cannot agree with ll;ese conceptions. In my specimen the rather long protuber- 

 ance is still quite prochondral, and just like the prochondral cardiobranchial end, 

 lies in the beginning of llie oesophagus. In the protuberance 1 can only discern 

 a processus nmscularis of the 7iii ceratobranchial, morphologically insignificant. 

 An intestinal protrusion which could also be considered as a Qtli branchial pouch, 

 is not present, and I must consider it as an artificial product in the specimen 

 of Braus. 



48* 



