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1Rote6 on tbc BreeMng Ibabita anb 

 Enibr^olog? of frogs/' 



By J. H. Morgan. 



THE following notes are the outcome of several years' obser- 

 vations on the breeding habits and stages in the develop- 

 ment of frogs. They are confessedly very incomplete, 

 having been collected rather as an amusement than with any desire 

 to increase our present knowledge of amphibian embryology. 

 Some older observations have been verified, and I believe a few 

 new observations made which perhaps are worth recording. From 

 many points of view I think the development of the frog is better 

 adapted to the need of students beginning the study of embryology 

 than the classical chick. Certainly this seems to be true if a 

 clearer knowledge of the phenomena of development in general is 

 desired, and not merely an introduction to human embryology — 

 the best excuse offered for presenting the hen's egg and chick, with 

 its mistifying yolk and white, and its incomprehensible (to begin- 

 ners) larval membranes. On the other hand, the ease with which 

 the young chicks are to be obtained at all seasons, makes a very 

 strong argument in their favour. Correspondingly, the difficulties 

 of removing the younger stages of the frog's egg from the sur- 

 rounding jelly has been a great drawback to the study. Appreci- 

 ating this last difficulty I have experimented, for several years, on 

 methods of removing these jelly membranes. At last I think I 

 have successfully solved the problem, and can now obtain, wnth 

 the greatest ease, the most difficult stages, which are also in perfect 

 histological condition. The method will be given in Section 9. 

 Clay models of the early stages of segmentation of the egg have 

 been a very useful addition in presenting to others the arrangement 

 of the cells. These, of course, should be copied from actual 

 eggs, and not from the perfectly regular (but entirely schematic) 

 figures of the ordinary text-books. 



The following subjects are touched upon: — (i) Time in laying, 

 and Localities; (2) Laying in confinement; (3) Polar Bodies ; 

 (4) Segmentation of the Eggs; (5) Orientation of the Egg; (6) En- 



* From American Naturalist, 189 1. 



International Journal of Microscopy and Natural Science. 

 Third Series. Vol. III. cc 



