1919] 



Cor't: Eggs and Miracidia of Human Schistosomes 



515 



(1913, p. 370, figs. 4, 6, 7) found either a spine or a thickening of the 

 shell in all the eggs which he examined, and concluded that it was a 

 constant feature. Looss (1911), in the examination of an extensive 

 series of eggs to determine whether the rudimentary spine is a constant 

 feature, found all degrees of variation and a considerable percentage 

 of eggs in which no spine was present. He therefore concluded that 

 the presence of this spine is a variable feature and not a specific 

 character. Wooley and Huffman (1911, p. 131), in examinations of 

 several hundred eggs of S. japonicum, found in no instance the least 

 appearance of a blunt protuberance or spine on the outer envelope 



Fio- 5. Microphotograph of miracidium of S. japonicum just after it has 

 escaped from the egg. Photographed by Dr. J. P. Hickey. 



of the egg. These observations suggest that the lateral spine of the 

 ova of S. japonicum is variable and cannot be considered as a specific 

 character. The surface of the shells of the eggs of this species which 

 I examined appeared to be covered with some sort of a sticky sub- 

 stance. This is shown by the fact that the egg never showed a clear- 

 cut outline as in S. mansoni (fig. 1), but always had particles of 

 debris adhering to it (fig. 5). 



When eggs were first examined fresh from the feces the miracidia, 

 which at this time completely filled the shells, were practically 

 motionless. After a few hours in fresh water the egg shell expanded, 

 leaving a considerable space between the shell and the miracidium, 

 which at this stage was moving actively. In this space were collected 

 granules and oil globules. The globules of oil were extruded from 



