SOME PROBLEMS OP EEPRODUOTION. 585 



mincing machine, which severed the investment, but did 

 not damage the embryos, which slipped through the holes in 

 the plate. Normal salt solution with a drop or two of 

 chloroform or a trace of thymol was then added, and the 

 whole shaken up in a stoppered jar. The envelopes entangled 

 air, and floated for the most part, while the heavier eggs 

 settled. These were drained and crushed, and then put in 

 the incubator in normal salt. The results were negative in 

 neutral or slightly alkaline solutions. In other experiments 

 the solutions were acidulated with 0*3 to 0'7 per cent. HCl. : 

 after incubation from halt" an hour to twenty hours it was 

 carefully neutralised and boiled to remove any acid albumen. 

 The filtrate, which came through quite clear, was then tested 

 by the biuret test, and iu the acid solutions gave a marked 

 reaction, with a trace of cupric sulphate and an excess of 

 caustic-soda solution ; that is, a pink colouration identical with 

 that of a few milligrammes of Schuchardt's peptone tested 

 in the same way. The quantities were not adequate to obtain 

 a sepai'atiou of peptone. In my first attempts I had used the 

 isolated ferment with blood-fibrin washed and boiled, and 

 also with boiled white of egg, and obtained the biuret 

 reaction as above. In this last series I relied on the abun- 

 dant finely divided proteid reserve granules of the embryo 

 itself as a source of peptone. I added some fibrin, but was 

 unable to ascertain any change in it. A similar isolated 

 batch of frog's eggs kept in a closed locker in the laboratory 

 in thymolised normal salt for three weeks not only gave no 

 peptone reaction, but failed to develop it on incubation. 



The technique that I have found most advantageous in 

 obtaining the extra-vascular blastoderm of chicks is to use 

 three- to four-day eggs. These are opened iu the usual way, 

 and the embryo removed by cutting with scissors just round 

 the sinus terminalis ; I then make a radial cut through the 

 remaining blastoderm aud vitelline membrane towards the 

 opposite pole, aud take them together in the forceps and 

 shake them apart, first in the dish of salt solution, where 1 

 uow remove the rest of the vitelline membrane. The blasto- 



VOL. 47, rAWT 4. — NEW SEKIKS. PI' 



