THE OVUM IN THE AMPHIBIA. 235 



No. 2. Fifty-eight ova were treated in exactly the same way, the interval being 

 about Jifteen seconds, and the whole time sixty. 



The seminal fluid employed was obtained from two males,the fluid used toNo.2 being 

 from a male which had paired four days before. Out of the whole number of eggs in 

 the two sets, amounting to one hundred and thirty-four, not one produced an embryo. 



No. 3. March 30, 1850. P.M. 5 h 5 m . Atmosphere 49 FAHR. 



One hundred and eight ova were passed on a moist surface, and were immediately 

 bathed with a thick solution of gum as above, and one second afterwards with seminal 

 fluid in water; the whole time occupied being sixty seconds. 



Segmentation took place in two, or at most only three of these ova, and even in 

 them very imperfectly, and much slower than in the corresponding ova of the set to 

 which they belonged, Set Q (p. 228-9), in which the fluid employed was obtained 

 from the testes of the Frog, and regarded as immature. 



No. 4. P.M. 5 h 18 m . Fifty-eight ova passed on a moistened surface were immediately 

 bathed with solution of gum, and one second afterwards with seminal fluid from the 

 same male as No. 3. The whole time occupied was forty-five seconds. 



The result of these two experiments, as compared with others of the set to which 

 they belonged, Set Q, was exceedingly curious. In the experiments with the nitrate 

 of potass as in Q 7, segmentation was carried to some extent, and the divisions of 

 the yelk were multiplied; while onlyfourova out of the fifty-eight, in this with gum, 

 gave any evidence of segmentation, and the process was not advanced further, either 

 in this or in the preceding experiment, No. 3, than to the completion of the primary 

 division of the yelk into two hemispheres. Thus not only was the process entirely 

 prevented in the great majority of the ova, but it was also very much retarded in 

 those in which it did take place, and this simply, as it appeared, by the mechanical 

 hindrance of the gum. Could it be that the effect was produced on the endosmic 

 action of the yelk ? These trials certainly appeared to show that the obstruction 

 was a mechanical one. I need scarcely remark, that no embryo was produced in 

 either of these experiments. 



No. 5. April 3, 1850. P.M. 3 h 25 m . Atmosphere 60 FAHR. 



Sixty-one ova were passed on a moistened surface and were immediately bathed with 

 impregnating fluid, and two seconds afterwards with a thick solution of gum-arabic, 

 and water was then added ; the whole time occupied being only twenty seconds. 



This experiment, when compared either with the four preceding ones, made at a 

 temperature of the atmosphere eleven degrees lower, or with that which follows, 

 No. 6, seems to point to the exact nature of the operation of the gum. At four hours 

 and Jive minutes from Jifteen to twenty ova had become segmented, and others were 

 in the act of becoming so. At seven hours and a half more than one-half of the 

 whole number had changed, and were perfectly healthy. Thus, in this case, in which 

 the gum was applied after the seminal fluid, impregnation occurred earlier than in 

 corresponding experiments of the same set, R 6, 7 and 8, with nitrate of potass, when 

 it happened in from four hours, and fourteen to twenty minutes. It was even as 



2 H 2 



