ink 1 Hi' UTTKUUDUTl i \\ i I >B v 



... lie> in the attachment of the dorsal !; 



which the intestine is connected to the \,-rteb la l column: the, 



trunk, on the contrary, i- imbedded in the ventral mesentery, as far, 

 at least, as >uch a structure is ever established in the Vertebrates; it 

 is almost completely metamorpho^-d into the heart. The latter is 

 therefore nothing else than a peculiarly developed pa- main 



blood vessel pn>\ ided \\ith especially strong nr 



In the first fundament of the heart there are two diliennt types 

 to be distinguished, one of which is present in Selachians, Ganoids, 

 Amphibia, and < -yclostomes. the other in Bony Fishes and the higher 

 Keptiles. Uirds, and Mammals. 



In the description of the first type I select as an example the 





Tig. 297. Cross section through the region of tha l.cart of an embryo of S*lamandr maculosa. 

 in which the fourth visceral arch is indicated, after 



; cm, visceral middle layer ; ep, epidermis ; Ih, anterior part of 



the body-cavity (pericardio-thoracic cavity) ; end, endocardium ; p, pericardium ; vkg, mmo 

 cardium anterius. 



development of the heart in the Amphibia, concerning which a 



detailed account ha> \vi ly been publislied ! 



In Amphibia the heart : lished very fa. 1 in the 



embryonic body, undern.ath the pharynx r : the head-gut 



L'07, 298). The embry,.i.i.- 1 o.ly ,-avity (tt) reaches into this 

 region, and in cross sections appears upon both sides of the nv 

 plant- as a narrow Bsmu . d halves of the body-cavity are 



>epai at ed from each other by a \entral mesentery (vhg), by means 

 of \\liich the under surface of the p'. the wall 



of the body. If we examine th- y more closely, we 



olerve that in its middle the two IUCM-M yrs from which it 



loped separate from each other and a :nall 



cavity (/<) to the primiii\ i 



