494 The Embryology of Hylocles Martinicensis 



the stage of hatching. In a longitudinal section of stage XV, it appears 

 as a branch of the cutaneous vessel. The pulmonary vein has not been 

 seen with certainty in any stage. As other vessels are clearly seen in the 

 preparation, it follows with great probability that the pulmonary vessels 

 are very small or wanting in embryonic stages. It will be remembered 

 that the lungs are small, and also that the left auricle is very small, and 

 the septum between it and the right auricle is late in developing." All 

 the facts then in connection with the morphology of the organs for 

 pulmonary respiration, go to show that the lungs are not of great func- 

 tional importance in embryonic stages. 



Lymph sinuses. — Sub-dermal lymph sinuses appear about stage X as 

 narrow spaces; by stage XIII they are enlarged into enormous sacs that 

 completely surround the animal (cf. Fig. M). They are separated by 

 narrow partitions, the principal sinuses being a dorsal, a ventral, and 

 lateral chambers. 



4. EXCRETORY AND REPRODUCTIVE ORGANS. 



The excretory system of Hylodes has been described by Selenka, 82, 

 from a reconstruction of one stage (about VI, judging from the figure 

 independently of the excretory system). He has added notes on a later 

 stage (about XIII), Selenka concludes that the pronephros degenerates 

 and the mesonepronephros appears early as compared with other amphibia, 

 and he associates this condition with the absence of gills, a combination 

 approaching the condition in Eeptiles. A comparison of this sort requires 

 further evidence from the study of the function of the organs. 



Field, 91, interprets Selenka's figures and description as showing that 

 the pronephros in the earlier stage appears already in a degenerate con- 

 dition, the collecting trunk being extended into irregular blind sacs 

 instead of convoluted, and opening directly into the anterior end of the 

 segmental duct. I have not made reconstructions of any stage, so that I 

 cannot judge of the accuracy of Selenka's ^ figures of the model, but in 



° In some of the lungless salamanders the auricle is small, the septum 

 between the auricles is incomplete, and the pulmonary vein is wanting. 



' The spinal cord in Salenka's cross section is in the shape of a cross, which 

 does not appear in my sections. His "J," called in the explanation of the 

 figure " Darm," is in the usual position of the heart, while the unlettered 

 space in the shading above it might well be the gut and rudiment of lungs. 

 Selenka mentions the lungs as present in the older embryo but wanting in 

 this. We have seen that the lung diverticulum is present even before VI. 

 I have found the degenerate glomus and rudiments of the ciliated funnels in 

 stages later than those in which Selenka mentions them. 



