474 The Embryology of Hylodes Martinicensis 



sity to Jamaica. The eggs were found at Bog Walk, on Blue Mountain 

 Peak, and at Port Antonio. On Blue Mountain Peak they occur at a 

 high elevation (about 6000 feet) in very damp localities, where the rain- 

 fall is very heavy. 



Andrews, 92, reports that " these tree-frogs are found all over the 

 island; at Port Antonio the breeding season seemed to be past July 20; 

 while at Manchioneal, specimens with very large ovarian eggs were taken 

 July 24." 



I wish also to thank Mr. E. L. Griffin for a set of eggs collected at 

 Cinchona (an elevation of 5100 feet). 



The eggs are found imbedded in a clear gelatinous substance, in masses 

 of about an inch in diameter, under loose stones or logs. During their 

 development, the adult frogs are to be found near them. It appears, 

 from the preserved material, that, in young stages at least, all the eggs 

 of a mass are uniformly advanced in development. 



I. EXTERNAL CHARACTERS. 



1. SEGMENTATION. 



The segmentation' stages that were obtained are sufficient to show the 

 general character of the division of the egg. In spite of the large quan- 

 tity of yolk, the segmentation is holoblastic. The first furrow usually 

 divides the egg in half, and the second comes in at right angles to the 

 first (Plate I, Pig. 1'), but in one egg the first furrow has cut off not 

 more than one-third of the egg from the rest. I have a number of eggs 

 in the two-celled stage in which the second furrow is deeply marked on 

 the upper pole, but extends only about half way around the egg (Figs. 1 

 and 2). I have no eggs that show how the third furrow comes in, or 

 whether it appears before the second furrow is completed. In later 

 stages the upper hemisphere divides more rapidly than the lower, as 

 shown in Figs. 3 and 4. It has recently been found in the large egg of 

 Desmognathus fusca, with a segmentation similar though even more un- 

 equal than that of Hylodes, that there is no equatorial furrow ; nor is the 

 third furrow equatorial in Triton cristatus, or constant in Salamandra 

 maculosa. Later stages of Hylodes (cf. Figs. 3 and 4) show the smaller 

 cells at the animal pole, the larger, yellower, more yoke-laden cells at the 

 other pole. The next link in the history (Fig. 5) is the stage where the 

 bastopore is closing in over the yolk-plug. 



^ The figures on the two plates are indicated by consecutive numbers, while 

 text figures are marked by a letter of the alphabet. 



