200 MR. NEWPORT ON THE IMPREGNATION OF 



minutes, and segmentation commenced at three hours and fifty -six minutes, and was 

 general in two minutes longer, at which time the temperature of the dark cupboard 

 in which the ova of this set of experiments were placed had been raised to 64 FAHR., 

 and that of the water they were contained in to 60 FAHR. 



In four days and a half, thirteen of these ova had produced embryos that were then 

 at the end of the third period of development, and on the eighth day the whole of 

 them had advanced to the period when they leave the ovum and attach themselves 

 to the exterior of the envelopes, the end of the fourth period of development. The 

 mean temperature of the locality in which these ova and the embryos produced from 

 them were placed, was about 60 FAHR. for the entire period of eight days. 



No. 2. P.M. l h 55 m . Forty-eight ova were touched once, as they passed from the 

 body of the frog, with a hair-pencil that had been dipped in a small quantity of 

 residual fluid retained with spermatozoa on a filter, in separating these from the fluid 

 portion of frog's semen, obtained and mixed with water forty minutes previous. 



The temperature of the cupboard having been raised as in No. 1, segmentation 

 commenced in three hours and Jifty-Jive minutes, bat was more general in four 

 hours. Many of these ova were only partially impregnated, and of consequence did 

 not produce embryos. Others passed through their changes, as in No. 1, and in 

 nearly similar periods of time. On the eighth day ten embryos had been produced. 



No. 3. P.M. 2 h 3 m . Fifty-seven ova were well bathed as they passed from the frog 

 with the fluid portion of semen that had passed through two filter papers and been 

 separated from most of the spermatozoa, and which when examined with the micro- 

 scope was found to contain only a very few of these bodies. 



No segmentation had taken place in any of these ova at the end of four hours and 

 jive minutes, but several had become ovoid. At four hours and thirty-seven minutes 

 segmentation had taken place in one ovum, and this alone produced an embryo. 



Set I, March 20, 1850. Atmosphere 48 FAHR. Water 47 FAHR. This set was 

 the counterpart of the preceding, Set H. 



No. 1. P.M. l h 15. Nineteen ova were treated in exactly the same way as in 

 No. 1 H, and at the expiration of ten minutes were removed to fresh water, and placed 

 where they were most exposed to light. 



No segmentation occurred in any of these ova until the expiration of seven hours 

 and forty-five minutes. The temperature of the room had then sunk to 47 FAHR., and 

 that of the water with the ova to 46 FAHR. All the changes in these ova were so 

 exceedingly slow, that at the end of the eighteenth hour, the temperature during 

 the interval becoming slightly further reduced, the segmentation of the yelk had not 

 advanced further than to the formation of the first equatorial and secondary median 

 furrows. On the fifth day the development of the germ had not proceeded further 

 than to the commencement of the formation of the area germinativa, the end of the 

 second period, the mean temperature during the interval having been 45'49 FAHR. ; 

 while the ova in No. 1 H had reached the end of the third period, the mean tern- 



