170 OXYURIS-LARVffi HATCHED IN THE HUMAN STOMACH, 



Furthermore, it was possiVde to adduce in favour of the second 

 view and against the first the following weighty considera- 

 tions : — 



1. The eggs found in faeces are generally in the first stages of 

 development. 



2. Such a mode of development as is supposed in the first 

 view would constitute an exception to the general rule for the 

 development of all entozoa, which is that the eggs or larvge pass 

 out to develop, to some extent at least, outside, and then to find, 

 after a more or less chequered career in the course of which they 

 may live for a time in a species difierent from that inhabited by 

 their adults, a new host of the original kind, 



3. Investigators who were generally free from O x y u r i s 

 having swallowed its eggs passed nearly mature worms after 

 about two weeks.* 



4. The larvie have been fouud in the duodenum and small 

 intestines, f 



5. Life-histories consonant with this second view have been 

 more or less perfectly established for some of the other species of 

 the genus O x y u r i s. | 



In fact these considerations have been thought by some to be 

 sufficiently weighty to warrant the assertion as an established 

 fact that the eggs of Oxyuris vermicularis first hatch 

 on being introduced into the human stomach, and that the larvae 

 on reaching the large intestine remain there to maturity. Such 

 an assertion is, however, not warranted by the above enumerated 

 considerations. 



This incomplete state of our knowledge concerning the develop- 

 ment of the Oxyuris of man led me to perform some experi- 

 ments. I placed twelve eggs of Oxyuris vermicularis 

 in a suction capsule, § sealed and partially exhausted of its air, and 



* Leuckart, " Parasiten d. Menschen." 



t Zenker, " Verhandl. der physik. med. Soc. zu Erlangen," 1872. 

 + Balfour, "Comp. Embryology," Vol. I. 



§ For description see " Two new instruments for biologists." Cobb, 

 Proceed, of Linn. Soc. of N.S.W., 1890, p. 157. 



