114 CONTAGIOUS DISEASES OF DOMESTICATED ANIMALS. 



beyoud the morula stage, as many of the eggs, particularly in the body 

 of the uterus, reveal the embryo iu process of development. Finally, 

 when a length of 20 to 22'"'" (.787-.8G6 inch) has been reached, eggs 

 containing fully formed embryos, rolled up and moving within their 

 narrow prison, are observed in the two divisions of the uterus. At this 

 ])eriod they may be forced out of the shell by pressure between two 

 glass slides ; the covers at the extremities detach themselves completely i 

 and the embryo emerges through either opening. When it leaves the 

 egg spontaneously, an act we have frequently' observed in the water, 

 the cephalic extremity always emerges first. 



The embrj'O, on leaving the egg, exactly resembles an agamous an- ^ 

 guillula (Plate II, Fig. 8, D). It is about .28""" (.011 inch) long, and \ 

 has a diameter of .013""" (.0005 inch) at the middle of the body. The 

 obtuse anterior extremity reveals a punctiform mouth, opening in the 

 middle of a papilla and continued into an oesophagus which occupies 

 the cephalic third of the body (Plate II, Fig. 9), and whose cavity is 

 distinguished as a very fine median line. This portion of the body is 

 clear ; the remaining two-thirds is filled with granulations or fine glob- 

 ules. The tail is conical and elongated. 



The embryos never leave the egg within the living body of the mother, 

 however complete the development of both may be. Only by the death of 

 the female and the destruction of its body are the ova placed at liberty. 

 The embryo will then emerge if the medium offers favorable conditions. 

 These are moisture and a temperature of at least 20^ C. (68° F.). These 

 facts we have frequently demonstrated by experiment and in other 

 ways. We have even found still attached to the trachea of pheasants i 

 destroyed by the gapes couples of dead syngames, with the soft, flaccid 

 body of the female, 24'"'" (.945 inch) long, opened in several places hy 

 the commencing process of maceration, through which a large number 

 of eggs had already escaped. It still contained manj- of them, each 

 inclosing a fully developed, very active embryo, but there was not a 

 single empty egg or free embryo in the entire cadaver. 



We have subjected the eggs to various conditions in order to deter- 

 mine those most favorable to the hatching of the young. 1. When in 

 a dry medium, as in sand, their contents dry up more rapidly in propor- 

 tion to the elevation of temperature. 2. In a moist state they preserve 

 their vitality for months, even for a year, without any perceptible modifi- 

 cation of their contents, if the temperature is kept below 15° C. (59° F.). 

 Under these conditions the contents finally undergo fatty degeneration 

 and are dissolved. 3. If, while in a humid state, the temperature be 

 raised to 20° C. (08° F.) or better, to 25° C. (77° F.), the embryo within 

 the egg moves and turns about and finally escapes by pushing away 

 one of the coverlets. 



The combined conditions of moisture and warmth are jmwerful enough 

 to bring about the development of the embryo and its escape from the 

 egg, in which at first no trace of it can be distinguished, and which con- 



