development of a xon-aquatic tadpole. 255 



The Eggs. 



The rounded or slightly oval eggs are laid in a cluster of 

 about twenty in a little chamber just below the surface of the 

 ground and communicating with the exterior by a small hole in 

 the roof. The eggs are large, and in my specimens range from 

 1"7 to 2"7 mm. in diameter. Each egg is enveloped by a stiff 

 mucilaginous coat which is firmly adherent to the coats of the 

 surrounding eggs. There is no perceptible vitelline membrane, 

 so that on removing the mucilaginous coat the naked egg, which 

 is very readily injured, is exposed. The eggs are yellowish white 

 without a trace of pigmentation. In sections through non- 

 segmented eggs I could detect only faint indications of a 

 protoplasmic pole. The egg consists at first of a coarsely granular 

 reticulum of protoplasm densely crowded with oval yolk- 

 globules of large size (average maximum diameter about 12 ^i). 

 The periphery of the egg is occupied by a thin layer of proto- 

 plasm containing fewer yolk-globules, and these are of a smaller 

 size. 



Segmentatiox and Early Stages. 



With the available material a full account of the segmenta- 

 tion is not possible. The earliest stage present in the series 

 shows four upper cell-masses or blastomeres elongated parallel 

 to a vertical furrow and continuous at their periphery with the 

 superficial protoplasmic layer surrounding the undivided yolk- 

 mass below (PI. II, fig. 1). These masses were moderately 

 sharply cut off horizontally from the relatively huge mass of 

 yolk, the vertical depth of the masses being only about one-sixth 

 of the diameter of the egg (Fig. la). The blastomeres consist 

 of denser protoplasm which, however, contains very numerous 

 yolk-globules of about one-half of the diameter of the ordinary 

 yolk-globules. The globules seem to have been reduced in size 

 b}' being dissolved away superficially for the fonnation of the 

 abundant protoplasm. The nuclei of these cells are large, oval, 

 l)ladder-like structures with a minimum amount of chromatin. 

 In none of the eggs was there any indication of vertical furrows 

 dividing the yolk-mass beneath, although in Hylodcs inartiniccnsis 

 ^liss Sampson describes the occurrence of such furrows. On 

 careful search I failed to find any nucleus at all in the yolk-mass, 

 but with the excessive amount of yolk it is not possible to be 

 entirely certain that none was present. At this stage segmenta- 

 tion is essentially meroblastic (PI. II, figs, la, lb). 



The only other early stage of development present in the 

 material shows a syncj^tial blastoderm of considerable depth with 

 numerous large nuclei, enveloping less than half of the surface 

 of the yolk-mass (Fig. 2). This syncytium is continuous with 

 the superficial layer of protoplasm surrounding the yolk-mass 

 (Fig. 2a). In this lajev occurred a few large nuclei. The 

 specimen showing this condition was obviously well preserved 

 and the absence of cell outlines cannot, I think, be attributed 

 to the action of the reagents employed. I consider it probable 



