EGGS. 83 



Pelodytes punctatus . . . 1,000 — 1,630 



Bana agilis 669 — 1,200 



Hyla arborea 800—1,000 



These results, however, do not always agree with 

 my own, as will be seen further on under the various 

 specific headings. 



In the Discoglossidx, which spawn two or three 

 times a vear, each brood consists of 300 to 1000 

 eggs in Discoglossus pictus, 80 to 100 in Bombinator 

 pachypus, and 20 to 90 in Alytes obstetricans. This 

 makes a probable maximum total of 3000 for the first 

 species, 300 for the second, and 270 for the third. 

 These numbers are, however, only approximative, for 

 no observer has yet been able to follow the spawning 

 of a given specimen throughout the year, and to record 

 the total number of eggs produced. 



Manipulating frogs' eggs is not easy, on account 

 of the sticky mucilage which adheres to the fingers or 

 instruments, and the counting is a very trying opera- 

 tion. Approximate computations are more easily 

 arrived at with the egg-strings of toads, which can be 

 divided into small portions, in which the eggs are 

 counted and the result multiplied by measuring the 

 length of the whole strings. 



Fig. 31. 



Cleavage of egg of Bana tempora/ria (after Ecker). 



After fecundation the vitelline sphere undergoes a 

 process of division, or segmentation, which can be 

 readily observed under the microscope or an ordinary 

 hand lens, and of which the above diagrammatic 



