A CONTRIBUTIOX TO THE EMBRYOLOGY OF HYLODES 

 MARTINICENSIS. 



BY 



LILIAN V. SAMPSON. 

 With 2 Plates and 17 Figures in the Text. 



TABLE OF CONTENTS. 



PAGE 



Intboduction 473 



I. External Ckaracteh.s 474 



1. Segmentation 474 



2. Embryonic stages 475 



II. Organogeny 477 



1. Origin of Organs 478 



2. Digestive Tract 478 



3. Heart and Blood-Vessels .' 489 



4. Excretory and Reproductive Organs 494 



5. Tail 495 



6. Dermal Fold. Beak. Sense Organs 496 



7. Comparison with Other Forms 497 



Summary 501 



For many years the general outline of the embryonic history of Hylodes 

 Martinicensis has been known. Since the early seventies, it has been 

 described as the West Indian tree-frog, with no aquatic tadpole stages, 

 but with an embryo developing within the egg membranes as far as the 

 adult form. — the embryo being provided with a large supply of yolk food, 

 being devoid of gills, but with a highly vascular and, therefore, it was 

 believed, respiratory tail. I am fortunate in having at my disposal a 

 good series of the eggs of Hylodes, from which I have studied the develop- 

 ment in more detail. 



I am glad to take this opportunity of acknowledging my indebtedness 

 to Professor T. H. Morgan for the material which he has collected and 

 obtained from others at different times, and for his help and sugges- 

 tions in the work. 



The eggs that I shall describe were collected by Professor Morgan 

 and Dr. Conant during two or three seasons, in the month of July, 

 on expeditions of the Marine Laboratory of the Johns Hopkins Univer- 

 American Journal of Anatomy. — Vol. III. 

 34 



