No. 2.] HEART OF LUNGLESS SALAMANDERS. 329 



TJie Heart of Liinglcss Salamanders. 



In the following description I shall use Salamandrina perspi- 

 cillata and Plethodon erythronotus as types ; other forms, how- 

 ever (Plethodon cinereus, Desmognathus fusca, Spelerpes 

 fuscus), have essentially the same structure. The prepara- 

 tion followed in Fig. 2, PI. XV, was treated as that used for 

 Fig. I. The sections represented in Figs. 6 and 7, PL XV, are 

 from a heart naturally injected with blood. 



In all of the lungless species mentioned above, the external 

 arrangement of the parts of the heart is very similar to that of 

 the heart of Salamandra maculosa ; but the pulmonary vein is 

 not to be seen, and a careful microscopic examination has failed 

 to reveal a trace of it. Similar results have been obtained by 

 Hopkins (14) and Bethge (i) with certain lungless forms. 



In the interior of the heart of Salamandrina still other modi- 

 fications of structure may be readily seen, the most important 

 of which is due to the disappearance of the septum atriorum, 

 which, like the pulmonary vein, seems to have left no trace of 

 its former existence. We find a well-developed sinus-atrium 

 valve, which extends from the sinus opening to the ventral 

 aspect of the ostium atrio-ventriculare ; its convex antero- 

 ventral margin, however, is fixed to the left atrial wall. The 

 posterior end of the valve is attached to the middle of the 

 lower atrio-ventricular valve, while its dorsal end extends from 

 the left atrial wall obliquely caudalward toward the sinus open- 

 ing, to whose dorsal margin it is fixed. This relation of the 

 valve to the sinus opening is essentially the same that we saw 

 in Salamandra, and has occasioned the remark of Hopkins, 

 that the sinus opening of the lungless salamander leads into 

 the left auricle. 



The conus of Salamandrina shows the same general structure 

 that we found in the conus of Salamandra. A spiral valve is 

 distinctly recognizable in the lungless form. 



Let us now consider the significance of the facts presented 

 above. We have found in the heart of lungless salamanders 

 certain changes of structure which must be attributed directly 

 or indirectly to the loss of lungs. One of these changes — 



