THE OVUM IN THE AMPHIBIA. 237 



Segmentation took place only, in two or three ova, at/owr hours and twenty-four 

 minutes, and at the end of ten days only three embryos had been produced. 



(b.) Starch. No. 10. P.M. l h 40. One hundred and Jifty-eight ova were passed 

 into a solution of starch in water, and at the end of ten seconds one-half of the whole 

 quantity of seminal fluid, obtained from a single frog, and previously mixed with 

 water, was added to them. 



After the ova had remained in the solution and been gently agitated during twenty 

 minutes, they were carefully washed and removed to clear water. 



At four hours and twenty-six minutes only a very few of these ova, not more than 

 eight or ten, had become segmented, notwithstanding the large quantity of recent 

 impregnating fluid that had been added to them. At the end of ten days only Jive 

 embryos had been produced. 



It was remarkable that very few of the ova in this experiment cohered together, as 

 the frog's ova almost invariably do when placed in fluid. On the contrary, most of 

 them remained separate and isolated, although their envelopes had imbibed water and 

 expanded to their usual extent in a similar space of time. 



No. 11. P.M. l h 47 m . Seventy-one ova were passed on a perfectly dry surface, and 

 immediately afterwards were covered, by means of a hair-pencil, with a thick solu- 

 tion of starch, and at the expiration of ten seconds with impregnating fluid, and water 

 was quickly added. 



The water was changed at the end of fifteen minutes. At four hours and twenty- 

 Jive minutes, only two or three ova had become segmented. At the end of ten days 

 three embryos had been produced. 



The concluding experiment with starch was the counterpart of No. 5, with gum. 



No. 12. P.M. l h 44 m . One hundred and nineteen ova were passed into water, with 

 which one-eighth part only of the seminal fluid, obtained from the Frog, had already 

 been mixed. Two seconds afterwards a solution of starch was added to these ova, 

 and at the end of sixteen minutes they were removed to clear water. 



In four hours and twenty-six minutes segmentation had commenced in many of these 

 ova. The exact number I omitted to ascertain. But the change had taken place in 

 a much shorter space of time, and was more general, although scarcely one-fourth 

 part of the quantity of seminal fluid that had been employed in No. 10 was used in 

 this case. Nevertheless, in ten days twelve embryos had been formed. 



This experiment, therefore, was quite confirmatory of the conclusions drawn from 

 its counterpart, No. 5, with gum, and Nos. 10 and 11 as fully bore out those deduced 

 from Nos. 1 to 5, with the same ; while the entire set seem to be in full accordance 

 with the already arrived at conclusion, that fecundation is commenced almost imme- 

 diately the fecundating body is in contact with the ovum. Thus, then, with regard 

 to the nature of impregnation, we seem to have obtained sufficient proof that the act 

 is effected through the agency of the spermatozoon, and not through that of the liquor 

 seminis, as was formerly supposed. 



