10 CARL GOTTFRIED HARTMAN 



Of these 415 eggs 230 were cut into serial sections five or six 

 micra thick, mounted and stained. A few were mounted in 

 balsam; some were lost in the handling and a few have been 

 retained in 80 per cent alcohol. Perhaps one-sixth or one-seventh 

 of the eggs taken from inseminated animals were clearly unfer- 

 tilized and showed signs of degeneration. 



Besides these, eggs were removed from 37 other females, so 

 that about one thousand ova were handled in the progress of 

 the work. In all of these last mentioned cases the eggs were 

 unfortunately degenerate, not being fertilized, and were therefore 

 usually not counted but discarded as worthless. Foetuses or 

 pouch young were secured in several dozen cases. 



Old degenerating eggs can easily be recognized. They are 

 large and the shell is opaque and covered with a white incrusta- 

 tion. Later the shell collapses and the egg becomes a shapeless 

 mass which sooner or later leaves the uterus. Young degenerate 

 eggs in which little change can be noted in the shell or in the albu- 

 men may usually be recognized by the flattening of the ovum in 

 the center. In side view the protoplasm (in which degeneration 

 first becomes apparent) assumes the shape of a crescent, to be 

 seen especially well in alcoholic specimens fixed in osmic acid 

 mixtures. 



A detailed account of each animal furnishing the eggs de- 

 scribed in this study follows. Unless the time of capture is indi- 

 cated it is understood that the animals were bred in captivity. 

 The captives were kept in cages from a few weeks to two months 

 or more. Nos. 40 to 58 were secured in 1914; Nos. 76 to 144 in 

 1915. 



2) History of animals. No. 21. Copulation January 3; killed Janu- 

 ary 6; ovarian eggs only. 



No 40. Placed with male January 31; killed February 6; 11 eggs; 

 unilaminar blastocysts with formation of entoderm ; three eggs unfer- 

 tilized. 



No. 43. Placed with male January 28. Male removed February 2; 

 killed February 7; 29 eggs: several late unilaminar blastocysts, mostly 

 later bilaminar blastocysts, 0.8 mm. to 1.0 mm. in diameter; 6 large 

 unfertilized eggs. 



No. 46. Killed February 8; ovulation recent, as indicated by promi- 

 nent and blood-shot stigmata on young corpora lutea; 21 small eggs; 



